Fused abrasive particles, abrasive articles, and methods of making and using the same

ABSTRACT

Fused abrasive particles comprising eutectic colonies. The fused abrasive particles can be incorporated into abrasive products such as coated abrasives, bonded abrasives, non-woven abrasives, and abrasive brushes.

This is a continuation-in-part of U.S. Ser. No. 09/496,638, filed Feb.2, 2000, abandoned the disclosure of which is incorporated herein byreference.

FIELD OF THE INVENTION

This invention pertains to fused abrasive particles and methods ofmaking the same. The fused abrasive particles can be incorporated into avariety of abrasive articles, including bonded abrasives, coatedabrasives, nonwoven abrasives, and abrasive brushes.

DESCRIPTION OF RELATED ART

There are a variety of abrasive particles (e.g., diamond particles,cubic boron nitride particles, fused abrasive particles, and sintered,ceramic abrasive particles (including sol-gel-derived abrasiveparticles) known in the art. In some abrading applications, the abrasiveparticles are used in loose form, while in others the particles areincorporated into abrasive products (e.g., coated abrasive products,bonded abrasive products, non-woven abrasive products, and abrasivebrushes). Criteria used in selecting abrasive particles used for aparticular abrading application include: abrading life, rate of cut,substrate surface finish, grinding efficiency, and product cost.

From about 1900 to about the mid-1980's, the premier abrasive particlesfor abrading applications such as those utilizing coated and bondedabrasive products were typically fused abrasive particles. There are twogeneral types of fused abrasive particles: (1) fused alpha aluminaabrasive particles (see, e.g., U.S. Pat. No. 1,161,620 (Coulter), U.S.Pat. No. 1,192,709 (Tone), U.S. Pat. No. 1,247,337 (Saunders et al.),U.S. Pat. No. 1,268,533 (Allen), and U.S. Pat. No. 2,424,645 (Baumann etal.)) and (2) fused (sometimes also referred to as “co-fused”)alumina-zirconia abrasive particles (see, e.g., U.S. Pat. No. 3,891,408(Rowse et al.), U.S. Pat. No. 3,781,172 (Pett et al.), U.S. Pat. No.3,893,826 (Quinan et al.), U.S. Pat. No. 4,126,429 (Watson), U.S. Pat.No. 4,457,767 (Poon et al.), and U.S. Pat. No. 5,143,522 (Gibson etal.))(also see, e.g., U.S. Pat. No. 5,023,212 (Dubots et. al) and U.S.Pat. No. 5,336,280 (Dubots et.al) which report the certain fusedoxynitride abrasive particles). Fused alumina abrasive particles aretypically made by charging a furnace with an alumina source such asaluminum ore or bauxite, as well as other desired additives, heating thematerial above its melting point, cooling the melt to provide asolidified mass, crushing the solidified mass into particles, and thenscreening and grading the particles to provide the desired abrasiveparticle size distribution. Fused alumina-zirconia abrasive particlesare typically made in a similar manner, except the furnace is chargedwith both an alumina source and a zirconia source, and the melt is morerapidly cooled than the melt used to make fused alumina abrasiveparticles. For fused alumina-zirconia abrasive particles, the amount ofalumina source is typically about 50-80 percent by weight, and theamount of zirconia, 50-20 percent by weight zirconia. The processes formaking the fused alumina and fused alumina abrasive particles mayinclude removal of impurities from the melt prior to the cooling step.

Although fused alpha alumina abrasive particles and fusedalumina-zirconia abrasive particles are still widely used in abradingapplications (including those utilizing coated and bonded abrasiveproducts, the premier abrasive particles for many abrading applicationssince about the mid-1980's are sol-gel-derived alpha alumina particles(see, e.g., U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat. No.4,518,397 (Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer etal.), U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671(Monroe et al.), U.S. Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No.4,960,441 (Pellow et al.), 5,139,978 (Wood), U.S. Pat. No. 5,201,916(Berg et al.), U.S. Pat. No. 5,366,523 (Rowenhorst et al.), U.S. Pat.No. 5,429,647 (Larmie), U.S. Pat. No. 5,547,479 (Conwell et al.), U.S.Pat. No. 5,498,269 (Larmie), U.S. Pat. No. 5,551,963 (Larmie), and U.S.Pat. No. 5,725,162 (Garg et al.)).

The sol-gel-derived alpha alumina abrasive particles may have amicrostructure made up of very fine alpha alumina crystallites, with orwithout the presence of secondary phases added. The grinding performanceof the sol-gel derived abrasive particles on metal, as measured, forexample, by life of abrasive products made with the abrasive particleswas dramatically longer than such products made from conventional fusedalumina abrasive particles.

Typically, the processes for making sol-gel-derived abrasive particlesare more complicated and expensive than the processes for makingconventional fused abrasive particles. In general, sol-gel-derivedabrasive particles are typically made by preparing a dispersion or solcomprising water, alumina monohydrate (boehmite), and optionallypeptizing agent (e.g., an acid such as nitric acid), gelling thedispersion, drying the gelled dispersion, crushing the dried dispersioninto particles, screening the particles to provide the desired sizedparticles, calcining the particles to remove volatiles, sintering thecalcined particles at a temperature below the melting point of alumina,and screening and grading the particles to provide the desired abrasiveparticle size distribution. Frequently a metal oxide modifier(s) isincorporated into the sintered abrasive particles to alter or otherwisemodify the physical properties and/or microstructure of the sinteredabrasive particles.

There are a variety of abrasive products (also referred to “abrasivearticles”) known in the art. Typically, abrasive products include binderand abrasive particles secured within the abrasive product by thebinder. Examples of abrasive products include: coated abrasive products,bonded abrasive products, nonwoven abrasive products, and abrasivebrushes.

Examples of bonded abrasive products include: grinding wheels, cutoffwheels, and honing stones). The main types of bonding systems used tomake bonded abrasive products are: resinoid, vitrified, and metal.Resinoid bonded abrasives utilize an organic binder system (e.g.,phenolic binder systems) to bond the abrasive particles together to formthe shaped mass (see, e.g., U.S. Pat. No. 4,741,743 (Narayanan et al.),U.S. Pat. No. 4,800,685 (Haynes et al.), U.S. Pat. No. 5,038,453(Narayanan et al.), and U.S. Pat. No. 5,110,332 (Narayanan et al.)).Another major type are vitrified wheels in which a glass binder systemis used to bond the abrasive particles together mass (see, e.g., U.S.Pat. No. 4,543,107 (Rue), U.S. Pat. No. 4,898,587 (Hay et al.), U.S.Pat. No. 4,997,461 (Markhoff-Matheny et al.), and U.S. Pat. No.5,863,308 (Qi et al.)). These glass bonds are usually matured attemperatures between 900° C. to 1300° C. Today vitrified wheels utilizeboth fused alumina and sol-gel-derived abrasive particles. However,fused alumina-zirconia is generally not incorporated into vitrifiedwheels due in part to the thermal stability of alumina-zirconia. At theelevated temperatures at which the glass bonds are matured, the physicalproperties of alumina-zirconia degrade, leading to a significantdecrease in their abrading performance. Metal bonded abrasive productstypically utilize sintered or plated metal to bond the abrasiveparticles.

The abrasive industry continues to desire abrasive particles andabrasive products that are easier to make, cheaper to make, and/orprovide performance advantage(s) over conventional abrasive particlesand products.

SUMMARY OF THE INVENTION

The present invention provides a fused, crystalline abrasive particlecomprising (preferably, at least 20, 30, 40, 50, 60, 70, 75, 80, 85, 90,95, 98, 99, or 100 percent by volume, based on the total metal oxidevolume of the particle) eutectic colonies, the colonies comprising athree-dimensional, interpenetrating network of first and secondcrystalline metal oxide phases, the first phase comprising at least oneof crystalline Al₂O₃ or a first, crystalline complex Al₂O₃.metal oxideand the second phase comprising a second, different, crystalline complexAl₂O₃.metal oxide. Preferably, fused, crystalline abrasive particlesaccording to the present invention preferably comprise, on a theoreticaloxide basis, at least 30 percent (or even at least 40, 50, 60, 70, or 80percent) by weight Al₂O₃, based on the total metal oxide content therespective particle.

In another aspect, the present invention provides a plurality ofparticles having a particle size distribution ranging from fine tocoarse, wherein at least a portion of the plurality of particles arefused, crystalline abrasive particles according to the presentinvention.

In another aspect, the present invention provides a method for makingfused, crystalline abrasive particles abrasive particles according tothe present invention, the method comprising:

melting at least one Al₂O₃ source and at least one reactive Al₂O₃ metaloxide source to provide a melt; and

converting the melt to fused, crystalline abrasive particles accordingto the present invention.

In this application:

“simple metal oxide” refers to a metal oxide comprised of a one or moreof the same metal element and oxygen (e.g., Al₂O₃, CeO₂, MgO, SiO₂, andY₂O₃);

“complex metal oxide” refers to a metal oxide comprised of two or moredifferent metal elements and oxygen (e.g., CeAl₁₁O₁₈, Dy₃Al₅O₁₂,MgAl₂O₄, and Y₃Al₅O₁₂);

“complex Al₂O₃.metal oxide” refers to a complex metal oxide comprisedof, on a theoretical oxide basis, Al₂O₃ and one or more metal elementsother than Al (e.g., CeAl₁₁O₁₈, Dy₃Al₅O₁₂, MgAl₂O₄, and Y₃Al₅O₁₂);

“complex Al₂O₃.Y₂O₃” refers to a complex metal oxide comprised of, on atheoretical oxide basis, Al₂O₃ and Y₂O₃ (e.g., Y₃Al₅O₁₂);

“complex Al₂O₃ rare earth oxide” refers to a complex metal oxidecomprised of, on a theoretical oxide basis, Al₂O₃ and rare earth oxide(e.g., CeAl₁₁O₁₈ and Dy₃Al₅O₁₂);

“reactive Al₂O₃.metal oxide” refers to a metal oxide other than Al₂O₃(e.g., Dy₂O₃ or Y₂O₃) that can react with Al₂O₃ to form at least onecomplex Al₂O₃.metal oxide;

“rare earth oxides” refer to, on a theoretical oxide basis, CeO₂, Dy₂O₃,Er₂O₃, Eu₂O₃, Gd₂O₃, Ho₂O₃, La₂O₃, Lu₂O₃, Nd₂O₃, Pr₆O₁₁, Sm₂O₃, Th₄O₇,Tm₂O₃, and Yb₂O₃;

“REO” means rare earth oxide; and

“particle size” is the longest dimension of a particle.

Fused abrasive particles according to the present invention can beincorporated into various abrasive products such as coated abrasives,bonded abrasives, nonwoven abrasives, and abrasive brushes.

The present invention also provides a method of abrading a surface, themethod comprising:

contacting at least one fused abrasive particle according to the presentinvention (preferably, a plurality of fused abrasive particles accordingto the present invention) with a surface of a workpiece; and

moving at least one of the fused abrasive particle according to thepresent invention or the surface relative to the other to abrade atleast a portion of the surface with the fused abrasive particleaccording to the present invention.

Preferred fused abrasive particles according to the present inventionprovide superior grinding performance as compared to current fusedabrasive particles. Preferred fused abrasive particles according to thepresent invention are sufficiently microstructurally and chemicallystable to allow them to be used with vitrified bonding systems withoutthe significant decrease in abrading performance of conventionalalumina-zirconia abrasive particles used with vitrified bonding systems.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary cross-sectional schematic view of a coatedabrasive article including fused abrasive particles according to thepresent invention;

FIG. 2 is a perspective view of a bonded abrasive article includingfused abrasive particles according to the present invention;

FIG. 3 is an enlarged schematic view of a nonwoven abrasive articleincluding fused abrasive particles according to the present invention;

FIG. 4 is a schematic of an exemplary portion of interpenetrating phasesin a eutectic colony;

FIG. 5 is a Differential thermal analysis (DTA) plot andThermogravimetric Analysis (TGA) plot of Example 1 fused material;

FIG. 6 is a DTA plot and TGA plot of Comparative Example D fusedmaterial;

FIG. 7 is a DTA plot and TGA plot of Comparative Example B abrasiveparticles;

FIGS. 8 and 9 are scanning electron photomicrographs of polishedcross-sections of Examples 1 and 2 fused material, respectively;

FIGS. 10 and 11 are scanning electron photomicrographs of polishedcross-sections of Comparative Examples B and D fused material,respectively;

FIGS. 12-14 are scanning electron photomicrographs of polishedcross-sections of Comparative Example B abrasive particles afterexposure to various heating conditions;

FIG. 15 is a scanning electron photomicrograph of a polishedcross-section of Comparative Example D fused material;

FIG. 16 is a scanning electron photomicrographs of polishedcross-section of Comparative Example D abrasive particle after exposureto a specified heating condition;

FIGS. 17 and 18 are scanning electron photomicrographs of polishedcross-sections of Example 4 and 5 abrasive particles, respectively;

FIG. 19 is a DTA plot and TGA plot of Example 5 abrasive particles;

FIGS. 20-26 are scanning electron photomicrographs of polishedcross-sections of Example 6-12 abrasive particles, respectively; and

FIG. 27 is a scanning electron photomicrograph of a polishedcross-section of Example 3 abrasive particles.

DETALED DESCRIPTION

Fused, crystalline abrasive particles according to the present inventionare comprised of eutectic colonies, wherein the colonies comprising athree-dimensional, interpenetrating network of first and secondcrystalline metal oxide phases.

Fused abrasive particles according to the present invention can be madeby heating the appropriate metal oxides sources to form a melt,preferably a homogenous melt, and then rapidly cooling the melt toprovide a solidified mass. The solidified mass is typically crushed toproduce the desired particle size distribution of abrasive particles.

More specifically, fused abrasive particles according to the presentinvention can be made by charging a furnace with sources of (on atheoretical oxide basis) Al₂O₃, other metal oxides (e.g., Y₂O₃, rareearth oxide(s), etc.), and other optional additives (e.g., processingaids). The metal oxide sources can be added to the furnace, for example,together and melted, or sequentially and melted.

For solidified melt material containing complex metal oxide(s), at leasta portion of the metal oxide present in the melted metal oxide sources(i.e., the melt) react to form complex metal oxide(s) during formationprocess of the solidified material. For example, an Al₂O₃ source and aY₂O₃ source may react to form Y₃Al₅O₁₂ (i.e., 5Al₂O₃+3Y₂O₃→2Y₃Al₅O₁₂,YAlO₃ (i.e., Al₂O₃+Y₂O₃→2YAlO₃), or Y₄Al₂O₉ (i.e., Al₂O₃+2Y₂O₃→Y₄Al₂O₉).Similarly, for example, an Al₂O₃ source and an Er₂O₃ or a Yb₂O₃ sourcemay react to form Er₃Al₅O₁₂ and Yb₃Al₅O₁₂, respectively. Further, forexample, an Al₂O₃ source and a Gd₂O₃ source may react to form GdAlO₃(i.e., Al₂O₃+Gd₂O₃→2GdAlO₃). Similarly, for example, an Al₂O₃ source anda CeO₂, Dy₂O₃, Eu₂O₃, La₂O₃, Nd₂O₃, Pr₂O₃, or Sm₂O₃ source may react toform CeAlO₃, Dy₃Al₅O₁₂, EuAlO₃, LaAlO₃, NdAlO₃, PrAlO₃, and SmAlO₃,respectively. Further, for example, an Al₂O₃ source and a La₂O₃ sourcemay react to form LaAlO₃ (i.e., Al₂O₃+La₂O₃→2LaAlO₃) and LaAl₁₁O₁₈(i.e., 11Al₂O₃+La₂O₃→2LaAl₁₁O₁₈). Similarly, for example, an Al₂O₃source and CeO₂, Eu₂O₃, Nd₂O₃, Pr₂O₃, or Sm₂O₃ source may react to formCeAl₁₁O₁₈, EuAl₁₁O₁₈, NdAl₁₁O₁₈, PrAl₁₁O₁₈, and SmAl₁₁O₁₈, respectively.

Depending upon the relative proportions of Al₂O₃ and Y₂O₃ or rare earthoxide, the resultant solidified material, and ultimately the fusedabrasive particles, comprises:

(a) crystalline Al₂O₃ together with crystalline Al₂O₃-complexAl₂O₃.metal oxide (complex Al₂O₃.metal oxide is, for example, Y₃Al₅O₁₂,Dy₃Al₅O₁₂, Er₃Al₅O₁₂, GdAlO₃, or Yb₃Al₅O₁₂) eutectic;

(b) Al₂O₃-complex Al₂O₃.metal oxide (again complex Al₂O₃.metal oxide is,for example, Y₃Al₅O₁₂, Dy₃Al₅O₁₂, Er₃Al₅O₁₂, GdAlO₃, or Yb₃Al₅O₁₂)eutectic; and/or

(c) crystalline complex Al₂O₃.metal oxide (again, complex Al₂O₃.metaloxide is, for example, Y₃Al₅O₁₂, Dy₃Al₅O₁₂, Er₃Al₅O₁₂, GdAlO₃, orYb₃Al₅O₁₂) together with crystalline Al₂O₃-complex Al₂O₃.metal oxide(again complex Al₂O₃.metal oxide is, for example, Y₃Al₅O₁₂, Dy₃Al₅O₁₂,Er₃Al₅O₁₂, GdAlO₃, or Yb₃Al₅O₁₂) eutectic.

If Al₂O₃ reacts with Y₂O₃ to form two complex metal oxides, theresulting solidified material, and ultimately the fused abrasiveparticles, depending upon the relative proportions of Al₂O₃ and Y₂O₃,comprises:

(a) first crystalline complex Al₂O₃.metal oxide (e.g., Y₃Al₅O₁₂ orYAlO₃) together with first crystalline complex Al₂O₃.metal oxide (again,e.g., Y₃Al₅O₁₂ or YAlO₃, respectively)-second, different, crystallinecomplex Al₂O₃.metal oxide (e.g., YAlO₃ or Y₄Al₂O₉, respectively)eutectic;

(b) first crystalline complex Al₂O₃.metal oxide (again, e.g., Y₃Al₅O₁₂or YAlO₃)-second, different, crystalline complex Al₂O₃.metal oxide(again, e.g., YAlO₃ or Y₄Al₂O₉, respectively) eutectic; and/or

(c) second, different, crystalline complex Al₂O₃.metal oxide (again,e.g., YAlO₃ or Y₄Al₂O₉) together with first crystalline complexAl₂O₃.metal oxide (again, e.g., Y₃Al₅O₁₂ or YAlO₃)-second, different,crystalline complex Al₂O₃.metal oxide (again, e.g., YAlO₃ or Y₄Al₂O₉,respectively) eutectic.

If Al₂O₃ reacts with rare earth oxide to form two complex metal oxides,the resulting solidified material, and ultimately the fused abrasiveparticles, depending upon the relative proportions of Al₂O₃ and rareearth oxide, comprises:

(a) first crystalline complex Al₂O₃.metal oxide (e.g., CeAlO₃, EuAlO₃,LaAlO₃, NdAlO₃, PrAlO₃, or SmAlO₃) together with first crystallinecomplex Al₂O₃.metal oxide (again, e.g., CeAlO₃, EuAlO₃, LaAlO₃, NdAlO₃,PrAlO₃, or SmAlO₃)-second, different, crystalline complex Al₂O₃.metaloxide (e.g., CeAl₁₁O₁₈, EuAl₁₁O₁₈, LaAl₁₁O₁₈, NdAl₁₁O₈, PrAl₁₁O₁₈, orSmAl₁₁O₁₈, respectively) eutectic;

(b) first crystalline complex Al₂O₃.metal oxide (again, e.g., CeAlO₃,EuAlO₃, LaAlO₃, NdAlO₃, PrAlO₃, or SmAlO₃)-second, different,crystalline complex Al₂O₃.metal oxide (again, e.g., CeAl₁₁O₁₈,EuAl₁₁O₁₈, LaAl₁₁O₁₈, NdAl₁₁O₁₈, PrAl₁₁O₁₈, or SmAl₁₁O₁₈, respectively)eutectic; and/or

(c) second, different, crystalline complex Al₂O₃.metal oxide (again,e.g., CeA,₁₁O₁₈, EuAl₁₁O₁₈, LaAl₁₁O₁₈, NdAl₁₁O₁₈, PrAl₁₁O₁₈, orSmAl₁₁O₁₈) together with first crystalline complex Al₂O₃.metal oxide(again, e.g., CeAlO₃, EuAlO₃, LaAlO₃, NdAlO₃, PrAlO₃, or SmAlO₃)-second,different, crystalline complex Al₂O₃.metal oxide (again, e.g.,CeAl₁₁O₁₈, EuAl₁₁O₁₈, LaAl₁₁O₁₈, NdAl₁₁O₁₈, PrAl₁₁O₁₈, or SmAl₁₁O₁₈,respectively) eutectic.

It is understood, however, the particular phases formed are dependentupon several factors including the melt composition and solidificationconditions. Typically it is preferred that the composition of the meltand the solidification conditions are such that a large portion of theresulting solidified material is occupied by eutectic (i.e., theformulation of the solidified material corresponds to close to eutecticproportions of the various metal oxide phases that present in thematerial). Although not wanting to be bound by theory, some metastableconditions during formation of the solidified material may lead to theformation of alternative eutectic. For example, if under normal, stableconditions the eutectic that forms is Al₂O₃/Y₃Al₅O₁₂, under somemetastable conditions Al₂O₃/YAlO₃ eutectic may form in place of, or inaddition to Al₂O₃/Y₃Al₅O₁₂ eutectic.

It is also with in the scope of the present invention to substitute aportion of the aluminum and/or other metal cations in the complexAl₂O₃.metal oxide with other cations. For example, a portion of the Alcations in a complex Al₂O₃.Y₂O₃ or Al₂O₃.REO may be substituted with atleast one cation of an element selected from the group consisting of:Cr, Ti, Sc, Fe, Mg, Ca, Si, Co, and combinations thereof. A portion ofthe Y cations in a complex Al₂O₃.Y₂O₃ may be substituted with at leastone cation of an element selected from the group consisting of: Ce, Dy,Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Th, Tm, Yb, Fe, Ti, Mn, V, Cr, Co,Ni, Cu, Mg, Ca, Sr, and combinations thereof. A portion of the rareearth cations in a complex Al₂O₃.REO may be substituted with at leastone cation of an element selected from the group consisting of: Y, Fe,Ti, Mn, V, Cr, Co, Ni, Cu, Mg, Ca, Sr, and combinations thereof.Similarly, it is also with in the scope of the present invention tosubstitute a portion of the aluminum cations in alumina. For example,Cr, Ti, Sc, Fe, Mg, Ca, Si, and Co can substitute for aluminum inalumina structure. The substitution of cations as described above mayaffect the properties (e.g. hardness, toughness, strength, thermalconductivity, etc.) of the abrasive particles.

Further, other eutectics will be apparent to those skilled in the artafter reviewing the present disclosure. For example, phase diagramsdepicting various eutectics, including additional eutectics for systemsdisclosed herein are known in the art.

Fused abrasive particles according to the present invention containingeutectic material typically are comprised of eutectic colonies. Anindividual colony contains generally homogeneous microstructuralcharacteristics (e.g., similar size and orientation of crystals ofconstituent phases within a colony). Typically, impurities, if present,in the fused, crystalline abrasive particles according to the presentinvention, tend to segregate to colony boundaries, and may be presentalone and/or as reaction products (e.g., as a complex Al₂O₃.metal oxideand/or a complex Y₂O₃.metal oxide) as crystalline and/or amorphous(glass) phase(s).

The constitution of eutectic colony may include: (a) two differentsimple metal oxides (e.g., an Al₂O₃ phase and a ZrO₂ phase), (b) asimple metal oxide (e.g., an Al₂O₃ phase) and a complex metal oxide(e.g., a GdAlO₃ phase), or (c) a two, different complex metal oxides(e.g., a LaAlO₃ phase and a LaAl₁₁O₁₈ phase). Examples of possibleeutectics for Al₂O₃ and Y₂O₃ include Al₂O₃—Y₃Al₅O₁₂ eutectic. Examplesof possible eutectics for Al₂O₃ and complex Al₂O₃.rare earth oxideinclude Al₂O₃—Dy₃Al₅O₁₂, Al₂O₃—Er₃AlP₅O₁₂, Al₂O₃—GdAlO₃, orAl₂O₃—Yb₃Al₅O₂ eutectics. Examples of possible eutectics for two,different complex metal oxide include a MgAl₂O₄—Y₃Al₅O₁₂ eutectic andReAlO₃—ReAl₁₁O₁₈ eutectics, where Re=Ce, Eu, La, Nd, Pr, or Sm.

In another aspect, the phases making up the eutectic colonies are (a)single crystals of two different metal oxides (e.g., single crystals ofeach of Al₂O₃ and Y₃Al₅O₁₂), (b) a single crystal of one metal oxide(e.g., single crystal Al₂O₃) and a plurality of crystals of a differentmetal oxide (e.g., polycrystalline Y₃Al₅O₁₂), or (c) two differentpolycrystalline metal oxides (e.g., polycrystalline Al₂O₃ andpolycrystalline Y₃Al₅O₁₂).

The colonies may be in any of a variety of shapes, typically, rangingfrom essentially spherical to columnar. The composition, phase, and/ormicrostructure (e.g., crystallinity (i.e., single crystal orpolycrystalline) and crystal size) of each colony may be the same ordifferent. The orientation of the crystals inside the colonies may varyfrom one colony to another. The phases making up a eutectic colony arepresent as an interpenetrating network(s). For example, referring toFIG. 4, eutectic colony 150 comprises first crystalline metal oxidephase 151 and second crystalline metal oxide phase 153. The twocontinuous phases form an entangled, three-dimensional network.

The number of colonies, their sizes and compositions are affected, forexample, by the melt composition and solidification conditions. Althoughnot wanting to be bound by theory, it is believed that the closer themelt composition is to the exact eutectic composition, the smaller thenumber of colonies that are formed. In another aspect, however, it isbelieved that slow, unidirectional solidification of the melt also tendsto minimize the number of colonies formed, while multidirectionalsolidification with relatively higher cooling rates tends to increasethe number of colonies formed. The solidification rate (i.e., coolingrate) of the melt and/or multidirectional solidification of the melttend to affect the type and/or number of microstructural imperfections(e.g., pores) present in the resulting fused abrasive particles. Forexample, although not wanting to be bound by theory, relatively rapidsolidification (i.e., solidification with relatively high cooling rates)and/or multidirectional solidification tend to lead to an increase inthe type and/or number of microstructural imperfections (e.g., pores)present in the resulting fused abrasive particles. Relatively slowsolidification, however, tends to lead to an increase in the size of thecolonies, and/or crystals present in the solidified material; althoughit may be possible through slow and controlled cooling, for example, toeliminate formation of colonies. Hence, in selecting the cooling rateand/or degree of multidirectional solidification, there may be a need toincrease or decrease the cooling rate to obtain the optimal balance ofdesirable and undesirable microstructural characteristics associatedwith the various cooling rates.

Further, for a given composition, the size of the colonies and phasespresent within the colonies tends to decrease as the cooling rate of themelt increases. Typically, the eutectic colonies in abrasive particlesaccording to the present invention are, on average, less than 100micrometers, preferably, less than 50 micrometers, wherein such size fora given colony is the average of the two largest dimensions measuredfrom a polished cross-section of the colony, as viewed with a scanningelectron microscope (SEM). Typically, the smallest dimension of thecrystalline phases making up the eutectic in a colony, as measured froma polished cross-section of the colony viewed with an SEM, is up to 10micrometers; preferably, up to 5 micrometers; more preferably, up to 1micrometer, or even up to 0.5 micrometer.

Some abrasive particles according to the present invention also includeprimary crystals of at least one of the metal oxide phases making up theeutectic constituent of the abrasive particle. For example, if theeutectic portion is made up of a LaAlO₃ phase and a LaAl₁₁O₁₈ phase, themicrostructure may also include primary crystals of LaAlO₃, which isbelieved to occur when the composition of the melt from which theabrasive particles are formed is rich in La₂O₃ (i.e., the melt contains,on a theoretical oxide basis, an excess of La₂O₃ relative to theeutectic); or if the eutectic is made up of a Yb₃Al₅O₁₂ phase, andAl₂O₃, the microstructure may also include primary crystals of Al₂O₃,which is believed to occur when the composition of the melt from whichthe abrasive particles are formed is rich in Al₂O₃ (i.e., the meltcontains, on a theoretical oxide basis, an excess of Al₂O₃ relative tothe eutectic).

The formation of the primary crystals is believed to result from adeviation from the particular eutectic proportions. The greater thedeviation, the larger the overall fraction of primary crystals. Theprimary crystals may be found in a variety of shapes, typically rangingfrom rod-like structures to dendritic-like structures. Although notwanting to be bound by theory, it is believed that the presence and/orformation of a primary crystal(s) adjacent to a colony may affect theresulting microstructure of the colony. In some cases it may beadvantageous (e.g., for increased abrading performance) to have primarycrystals (e.g., primary Al₂O₃ crystals) present in the abrasiveparticles. It is also believed, however, that the abrading performanceof an abrasive particle tends to decrease as the size of the primarycrystals increase.

Further, although not wanting to be bound by theory, it is believed thatsmall additions (e.g., less than 5 percent by weight) of metal oxidesother than those making up the eutectic may affect colony boundaries,and in turn affect properties (e.g., hardness and toughness) of theabrasive particle.

Sources of (on a theoretical oxide basis) Al₂O₃ for making abrasiveparticles according to the present invention include those known in theart for making conventional fused alumina and alumina-zirconia abrasiveparticles. Commercially available Al₂O₃ sources include bauxite(including both natural occurring bauxite and synthetically producedbauxite), calcined bauxite, hydrated aluminas (e.g., boehmite, andgibbsite), Bayer process alumina, aluminum ore, gamma alumina, alphaalumina, aluminum salts, aluminum nitrates, and combinations thereof.The Al₂O₃ source may contain, or only provide, Al₂O₃. Alternatively, theAl₂O₃ source may contain, or provide Al₂O₃, as well as one or more metaloxides other than Al₂O₃ (including materials of or containing complexAl₂O₃.metal oxides (e.g., Dy₃Al₅O₁₂, Y₃Al₅O₁₂, CeAl₁₁O₁₈, etc.)).

Preferred metal oxides in addition to the Al₂O₃ (i.e., preferred “metaloxides other than Al₂O₃”) include Y₂O₃ and rare earth oxide.

Commercially available sources of (on a theoretical oxide basis) Y₂O₃for making abrasive particles according to the present invention includeyttrium oxide powders, yttrium, yttrium-containing ores, and yttriumsalts (e.g., yttrium carbonates, nitrates, chlorides, hydroxides, andcombinations thereof). The Y₂O₃ source may contain, or only provide,Y₂O₃. Alternatively, the Y₂O₃ source may contain, or provide Y₂O₃, aswell as one or more metal oxides other than Y₂O₃ (including materials ofor containing complex Y₂O₃.metal oxides (e.g., Y₃Al₅O₁₂)).

Commercially available sources of rare earth oxides for making abrasiveparticles according to the present invention include rare earth oxidepowders, rare earth metals, rare earth-containing ores (e.g., bastnasiteand monazite), rare earth salts, rare earth nitrates, and rare earthcarbonates. The rare earth oxide(s) source may contain, or only provide,rare earth oxide(s). Alternatively, the rare earth oxide(s) source maycontain, or provide rare earth oxide(s), as well as one or more metaloxides other than rare earth oxide(s) (including materials of orcontaining complex rare earth oxide * other metal oxides (e.g.,Dy₃Al₅O₁₂, CeAl₁₁O₁₈, etc.)).

The addition of certain metal oxides may alter the crystalline structureor microstructure of the resulting fused abrasive particles. Forexample, although not wishing to be bound by any theory, it is theorizedthat certain metal oxides or metal oxide containing compounds (even whenused in relatively small amounts, for example, even 0.01 to 5 percent byweight, based on the total metal oxide content of the fused abrasiveparticle) may be present at the boundaries between the eutecticcolonies. The presence of these metal oxides, which may be in the formof reaction products together or with the Al₂O₃ may affect the fracturecharacteristics and/or microstructure of the fused abrasive particles,and/or may affect the grinding characteristics of the abrasiveparticles. Certain metal oxides may also act as a processing aid, forexample, to increase the density of the fused abrasive particles, bydecreasing the size and/or number of pores in the fused abrasiveparticles. Certain metal oxides may also act as a processing aid, forexample, to increase or decrease the effective melting temperature ofthe melt. Thus certain metal oxides may be added for processing reasons.

Fused abrasive particles according to the present invention typicallycomprise less than 50 percent by weight (more typically, less than 20percent by weight; in some cases in the range from 0.01 to 5 percent byweight, in other cases from 0.1 to 1 percent by weight) of metals oxides(on a theoretical oxide basis) other than eutectic forming metal oxides,based on the total metal oxide content of the respective abrasiveparticle. Sources of the metal oxides other than Al₂O₃, Y₂O₃, and rareearth oxides are also readily commercially available.

Examples of metal oxides other than Al₂O₃, Y₂O₃, rare earth oxidesinclude, on a theoretical oxide basis, BaO, CaO, Cr₂O₃, CoO, Fe₂O₃,HfO₂, Li₂O, MgO, MnO, NiO, SiO₂, TiO₂, Na₂O, Sc₂O₃, SrO, V₂O₃, ZnO,ZrO₂, and combinations thereof.

Metal oxide sources for making abrasive particles according to thepresent invention also include fused abrasive particles (e.g., fusedalumina abrasive particles) or other fused material (e.g., fused aluminamaterial) having the same composition or different composition(s), whichtogether with remaining metal oxide sources, provide the desiredcomposition of the fused abrasive particles.

A reducing agent, such as a carbon source may be added to reduceimpurities during the melting process. Examples of carbon sourcesinclude: coal, graphite, petroleum coke, or the like. Typically, theamount of carbon included in the charge to the furnace is up 5% byweight of the charge; more typically, up to 3% by weight, and moretypically, up to 2% by weight. Iron may also be added to the furnacecharge to aid in the removal of impurities. The iron can combine withthe impurities to make a material that can be removed magnetically, forexample, from the melt or crushed solidified material.

It is also within the scope of the present invention to include metalborides, carbides, nitrides, and combinations thereof in the fused,crystalline abrasive particles according to the present invention. Suchmaterials may even be present within (e.g., as inclusions) the eutecticmaterial. Examples of metal borides, carbides, and nitrides may includetitanium diboride, aluminum carbide, aluminum nitride, titanium carbide,titanium nitride, silicon carbide, boron carbide, boron nitride,titanium carbide, titanium nitride, silicon carbide, boron carbide, andboron nitride. Such materials are known in the art, and are commerciallyavailable.

The particular selection of metal oxide sources and other additives formaking fused abrasive particles according to the present inventiontypically takes into account, for example, the desired composition andmicrostructure of the resulting abrasive particles, the desired physicalproperties (e.g., hardness or toughness) of the resulting abrasiveparticles, avoiding or minimizing the presence of undesirableimpurities, the desired grinding characteristics of the resultingabrasive particles, and/or the particular process (including equipmentand any purification of the raw materials before and/or during fusionand/or solidification) being used to prepare the abrasive particles.

The metal oxide sources and other additives can be in any form suitableto the process and equipment being used to make the abrasive particles.The raw materials can be fused using techniques and equipment known inthe art for making conventional fused alumina and alumina-zirconiaabrasive particles (see, e.g., U.S. Pat. No. 3,781,172 (Pett et al.),U.S. Pat. No. 3,891,408 (Rowse et al.), U.S. Pat. No. 4,035,162(Brothers et al.), U.S. Pat. No. 4,070,796 (Scott), U.S. Pat. No.4,073,096 (Ueltz et al.), U.S. Pat. No. 4,126,429 (Watson), U.S. Pat.No. 4,457,767 (Poon et al.), U.S. Pat. No. 5,143,522 (Gibson et al.),and Re. 31,128 (Walker et al.), the disclosures of which areincorporated herein by reference).

Examples of furnaces for melting the metal oxide sources and otheradditives include arc furnaces, pig furnaces, arc tapping furnaces,electric furnaces, electric arc furnaces, and gas fired furnaces.Suitable electric furnaces include those in which the electrodes arearranged to create a “kissing arc”, wherein the lower tip of theelectrodes are not in contact within the molten mass, as well as thosein which the electrodes are submerged in the molten mass to provideresistance heating via current passing through the melt.

The furnace may have a lining (sometimes referred to as a “shell” or“skeleton”) that covers the inside of the furnace walls. The lining maybe made from a material dissimilar to the fused abrasive particlecomposition. Typically, however it is preferred that the furnace liningis made from a composition or material similar, sometimes nearlyidentical or identical to the composition of the fused abrasiveparticle. Thus during processing, if the outer (exposed) surface of thelining melts, the potential contamination of the melt is reduced orminimized.

For some metal oxide sources and other additives, it may also bedesirable to preheat feed prior to charging it into the furnace, orotherwise combining it with other metal oxide sources and otheradditives. For example, if carbonate, nitrate or other salts are used asthe metal oxide source, it may be desirable to calcine (e.g., by heatingthem in air at about 400-1000° C.) such materials prior to adding themwith the other metal oxide source materials.

Generally, the metal oxide sources and other additives, if present, areheated to a molten state, and mixed until the melt is homogenous.Typically, the melt is heated to and held at a temperature at least 50°C. (preferably, at least 100° C.) above the melting point of the melt.If the temperature of the melt is too low, the viscosity of the melt maybe undesirably too high, making it more difficult to homogenize thevarious metal oxide sources and other additives making up the melt, orto pour or otherwise transfer the melt from the furnace. If thetemperature of the melt is too high temperature, and/or the melt heatedfor too long, energy will be wasted, and there may be undesirablevolatilization of components of the melt as well.

In some cases, it may be desirable, to mix, or otherwise blend the metaloxide sources and other additives (e.g., volatile components (e.g.,water or organic solvent) which may assist in forming a homogenousmixture or blend), if present, together prior to forming the melt. Forexample, particulate metal oxide sources can be milled (e.g., ballmilled) to both mix the materials together, as well as reduce the sizeof the particulate material. Other techniques for mixing or blending themetal oxide sources and other additives, if present, together prior toforming the melt include high shear mixers, paddle mixers, V-blenders,tumblers, and the like. Milling times may range from several minutes toseveral hours, or even days. Optionally, fugitive materials such aswater and organic solvents may be removed from the mixture or blend ofmetal oxide sources and other additives, for example, by heating, priorto forming the melt. For ease of handling, the metal oxide sources andother additives may also be agglomerated prior to charging them to thefurnace.

The atmosphere over the melt may be at atmospheric pressure, a pressureabove atmospheric pressure, or a pressure below atmospheric pressure,although a pressure below atmospheric pressure may be preferred in orderto reduce the number of pores in the resulting solidified material. Theatmosphere over the melt may also be controlled to provide an oxidizing,reducing or inert atmosphere which may affect the melt chemistry.

Reducing conditions during melting may aid in purifying the melt. Inaddition to, or alternatively to, adding a reducing agent to the melt,suitable reducing conditions may be obtained using carbon electrodeswith an electric arc melting furnace. Under suitable reducingconditions, some impurities (e.g., silica, iron oxide, and titania) willconvert to their respective molten metallic form, leading to a higherspecific gravity for the melt. Such free metal(s) impurities would thentend to sink to the bottom of the furnace.

In another aspect, it may be desired to oxidize free metal present inthe melt before the melt is cooled (e.g., before pouring the melt fromthe furnace). For example, an oxygen lance(s) may be inserted into themelt just prior to pouring the melt from the furnace (see, e.g., U.S.Pat. No. 960,712, the disclosure of which is incorporated herein byreference).

The melt can be cooled using any of a variety of techniques known in theart. Typically the furnace containing the melt is capable of beingtilted such that the melt can be poured over or into a heat sink.Generally, the resulting solidified material is larger in size than thedesired abrasive particles. Examples of heat sinks include metallicballs (e.g., cast iron or carbon steel balls), metallic rods, metallicplates, metallic rolls, and the like. In some instances, these heat sinkmaterials may be internally cooled (e.g., water-cooled or a suitablerefrigerant) to achieve fast cooling rates. The heat sink material mayalso be pieces of pre-fused abrasive particles (having the same or adifferent composition being solidified) or other refractory material.

Further with regard to heat sinks, the melt can be cooled by pouring themelt over and in between a plurality of metallic balls. The ballstypically range in diameter from about 1 to 50 cm, more typically 5 to25 cm. The melt may also be cooled using book molds. Suitable book moldsconsist of a plurality of thin plates (e.g., metallic or graphiteplates) that are spaced relatively close together. The plates areusually spaced less than 10 cm apart, typically less than 5 cm, andpreferably less than 1 cm apart. The melt may also be poured intographite or cast iron molds to form slabs. It is generally preferredthat such “slabs” be relatively thin so as to achieve faster coolingrates.

The cooling rate is believed to affect the microstructure and physicalproperties of the solidified material, and thus the fused abrasiveparticles. Preferably, the melt is rapidly cooled as the size of thecrystalline phases of the solidified material generally decreases as thecooling rate increase. Preferred cooling rates are at least 500°C./min.; more preferably, at least 1000° C./min; and even morepreferably, at least 1500° C./min. The cooling rate may depend uponseveral factors including the chemistry of the melt, the melting pointof the melt, the type of heat sink, and the heat sink material.

Rapid cooling may also be conducted under controlled atmospheres, suchas a reducing, neutral or oxidizing environment to maintain and/orinfluence the desired crystalline phases, oxidation states, etc. duringcooling.

Additional details on cooling a melt can be found, for example, in U.S.Pat. No. Re 31,128 (Walker et al.), U.S. Pat. No. 3,781,172 (Pett etal.), U.S. Pat. No. 4,070,796 (Scott et al.), U.S. Pat. No. 4,194,887(Ueltz et al.), U.S. Pat. No. 4,415,510 (Richmond), U.S. Pat. No.4,439,845 (Richmond), and U.S. Pat. No. 5,143,522 (Gibson et al.), thedisclosures of which are incorporated herein by reference.

The resulting (solidified) fused material(s) is typically larger in sizethan that desired for the abrasive particle(s). The fused material canbe, and typically is, converted into smaller pieces using crushingand/or comminuting techniques known in the art, including roll crushing,canary milling, jaw crushing, hammer milling, ball milling, jet milling,impact crushing, and the like. In some instances, it is desired to havetwo or multiple crushing steps. For example after the molten material issolidified, it may be in the form of a relatively large mass structure(e.g., a diameter greater than 5 cm. The first crushing step may involvecrushing these relatively large masses or “chunks” to form smallerpieces. This crushing of these chunks may be accomplished with a hammermill, impact crusher or jaw crusher. These smaller pieces may then besubsequently crushed to produce the desired particle size distribution.In order to produce the desired particle size distribution (sometimesreferred to as grit size or grade), it may be necessary to performmultiple crushing steps. In general the crushing conditions areoptimized to achieve the desired particle shape(s) and particle sizedistribution.

The shape of fused abrasive particles according to the present inventiondepends, for example, on the composition and/or microstructure of theabrasive particles, the geometry in which it was cooled, and the mannerin which the solidified material is crushed (i.e., the crushingtechnique used). In general, where a “blocky” shape is preferred, moreenergy may be employed to achieve this shape. Conversely, where a“sharp” shape is preferred, less energy may be employed to achieve thisshape. The crushing technique may also be changed to achieve differentdesired shapes. Alternatively, abrasive particles may be directly formedinto desired shapes by pouring or forming the melt into a mold.

The shape of the abrasive particles may be measured by varioustechniques known in the art, including bulk density and aspect ratio.The larger the abrasive particle size, the higher the bulk density dueto the increased mass associated with larger particle sizes. Thus, whencomparing bulk densities, the comparison should be made on abrasiveparticles having essentially the same particle size. In general, thelarger the bulk density number, the “blockier” the abrasive particle isconsidered to be. Conversely the smaller the bulk density number, the“sharper” the abrasive particle is considered to be. Another way tomeasure sharpness is through an aspect ratio. The aspect ratio of agrade 36 for example, may range from about 1:1 to about 3:1, typicallyabout 1.2:1 to 2:1.

The bulk density of the abrasive particles can be measured in accordancewith ANSI Standard B74.4-1992 (1992), the disclosure of which isincorporated herein by reference. In general, the bulk density ismeasured by pouring the abrasive particles sample through a funnel sothat the abrasive particles traverses through the funnel in a freeflowing manner. Immediately underneath the funnel is a collection device(typically a graduated cylinder). A predetermined volume of abrasiveparticles are collected and then weighed. The bulk density is calculatedin terms of weight/volume.

Abrasive particles according to the present invention can be screenedand graded using techniques well known in the art, including the use ofindustry recognized grading standards such as ANSI (American NationalStandard Institute), FEPA (Federation Europeenne des Fabricants deProducts Abrasifs), and JIS (Japanese Industrial Standard). Abrasiveparticles according to the present invention may be used in a wide rangeof particle sizes, typically ranging in size from about 0.1 to about5000 micrometers, more typically from about 1 to about 2000 micrometers;preferably from about 5 to about 1500 micrometers, more preferably fromabout 100 to about 1500 micrometers.

In a given particle size distribution, there will be a range of particlesizes, from coarse particles fine particles. In the abrasive art thisrange is sometimes referred to as a “coarse”, “control” and “fine”fractions. Abrasive particles graded according to industry acceptedgrading standards specify the particle size distribution for eachnominal grade within numerical limits. Such industry accepted gradingstandards include those known as the American National StandardsInstitute, Inc. (ANSI) standards, Federation of European Producers ofAbrasive Products (FEPA) standards, and Japanese Industrial Standard(JIS) standards. ANSI grade designations (i.e., specified nominalgrades) include: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180,ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI600. Preferred ANSI grades comprising abrasive particles according tothe present invention are ANSI 8-220. FEPA grade designations includeP8, P12, P16, P24, P36, P40, P50, P60, P80, P100, P120, P150, P180,P220, P320, P400, P500, 600, P800, P1000, and P1200. Preferred FEPAgrades comprising abrasive particles according to the present inventionare P12-P220. JIS grade designations include JIS8, JIS12, JIS16, JIS24,JIS36, JIS46, JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JIS2200, JIS240, JIS280, JIS320, JIS360, JIS400, JIS400, JIS600, JIS800, JIS1000,JIS1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS10,000. PreferredJIS grades comprising abrasive particles according to the presentinvention are JIS8-220.

After crushing and screening, there will typically be a multitude ofdifferent abrasive particle size distributions or grades. Thesemultitudes of grades may not match a manufacturer's or supplier's needsat that particular time. To minimize inventory, it is possible torecycle the off demand grades back into the molten mass. This recyclingmay occur after the crushing step, where the particles are in largechunks or smaller pieces (sometimes referred to as “fines”) that havenot been screened to a particular distribution. A charge to the furnacefor making fused abrasive particles according to the present inventionmay consist of anywhere from 0 to 100% by weight recycled fused abrasiveparticles, typically between 0 to 50% by weight.

Typically, the true density, sometimes referred to as specific gravity,of fused abrasive particles according to the present invention istypically at least 80% of theoretical density, although abrasiveparticles with a lower true density may also be useful in abrasiveapplications. Preferably, the true density of fused abrasive particlesaccording to the present invention is at least 85% of theoreticaldensity, more preferably at least 90% of theoretical density, and evenmore preferably at least 95% of theoretical density.

Typically, fused abrasive particles according to the present inventionmay have an average hardness (i.e., resistance to deformation; alsoreferred to as (“microhardness”) of at least 11 GPa; preferably, atleast 12, 13, or 14 GPa, more preferably, at least 15 GPa, and even morepreferably, at least 16 GPa, at least 17 GPa, or even at least 18 GPa.In another aspect, fused abrasive particles according to the presentinvention may have an average toughness (i.e., resistance to fracture)of at least 2.0 MPa m^(½); preferably at least 2.5 MPa m^(½), morepreferably at least 3.0 MPa m^(½), and even more preferably, at least3.3 MPa m^(½), at least 3.5 MPa m^(½), or even at least 3.8 MPa m^(½).

It is also within the scope of the present invention to provide asurface coating on the fused abrasive particles. Surface coatings areknown, for example, to improve the adhesion between the abrasiveparticles and the binder material in the abrasive article. Such surfacecoatings are described, for example, in U.S. Pat. No. 1,910,444(Nicholson), U.S. Pat. No. 3,041,156 (Rowse et al.), U.S. Pat. No.4,997,461 (Markhoff-Matheny et al.), U.S. Pat. No. 5,009,675 (Kunz etal.), U.S. Pat. No. 5,042,991 (Kunz et al.), and U.S. Pat. No. 5,085,671(Martin et al.), the disclosures of which are incorporated herein byreference. Further, in some instances, the addition of the coatingimproves the abrading characteristics of the abrasive particles.Alternatively the surface coating may improve adhesion between theabrasive particle of the invention and the binder.

Likewise after the abrasive particles are produced, it may be furtherheat-treated to improve their physical properties and/or grindingperformance. This heat-treating process may occur in an oxidizingatmosphere. Typically this heat-treating process occurs at a temperaturebetween about 1100° C. to 1600° C., usually between 1200° C. to 1400° C.The time may range from about 1 minute to days, usually between about 5minutes to 1 hour.

Other suitable preparation techniques for making fused abrasiveparticles according to the present invention may be apparent to thoseskilled in the art after reviewing the disclosure herein, as well as,for example, applications having U.S. Ser. Nos. 09,495,978, 09/496,422,09/496,638, and 09/496,713, each filed on Feb. 2, 2000, and Ser. Nos.9/618,876, 09/618,879, 09/619,106, 09/619,192, 09/619,215 09/619,289,09/619,563, 09/619,729, 09/619,744, and 09/620,262, each filed on thesame date as the instant application, the disclosure of which are allincorporated herein by reference

Preferred abrasive particles according to the present invention arethermally stable at elevated temperatures, as compared to conventionalfused alumina-zirconia materials (including alumina-zirconia abrasiveparticles available from Norton Company, Worcester, Mass. under thetrade designation “NORZON”). When alumina-zirconia eutectic abrasiveparticles available from Norton Company, Worcester, Mass. under thetrade designation “NORZON, are heated in air, for example, to at leastabout 350° C., typically at least a portion of the zirconia undergoes atetragonal and/or cubic to monoclinic phase transformation. This phasetransformation is usually detrimental to the structural integrity of thealumina-zirconia material because it involves volume changes to thezirconia crystalline phases. Further, such phase transformations havebeen observed to occur preferentially at the boundaries of eutecticcolonies, which thereby tend to weaken the boundaries, and which in turntend to lead to significant degradation of mechanical properties (i.e.,hardness, strength, etc.) of the material. In addition, variousimpurities, which are typically segregated during solidification of themelt into the eutectic colonies boundaries may also undergo volumetricstructural changes (e.g., due to oxidation), leading to furtherdegradation of mechanical properties (i.e., hardness, strength, etc.) ofthe material.

By contrast, preferred abrasive particles according to the presentinvention typically do not exhibit phase transformations of the eutecticphases when heated up to 1000° C. (in some cases even up to 1400° C.) inair, and thus are thermally stable. Although not wishing to be bound byany theory, it is believed that this thermal stability allows suchabrasive particle to be incorporated into vitrified bonded abrasives.

The thermal stability of certain preferred abrasive particles accordingto the present invention may be measured or illustrated using a varietyof different techniques, including: Differential Thermal Analysis (DTA),Thermogravimetric Analysis (TGA), X-ray diffraction, hardnessmeasurements, microstructure analysis, color change, and interactionwith glass bonds. The thermal stability of the abrasive particles may bedependent, for example, upon the composition, particle chemistry, andprocessing conditions.

In one test for measuring the thermal stability of certain preferredabrasive particles according to the present invention, the averagehardness of the abrasive particles is measured before and after beingheated in air at 1000° C. in air for 4 hours (see Example 3 (below) fora more complete description of the test). Although there may be somedegradation of the average microhardness after being heated for 4 hoursin air at 1000° C., the average hardness of certain preferred abrasiveparticles according to the present invention after being heated for 4hours in air at 1000° C. are at least 85% (preferably at least 90%, morepreferably at least 95%, and even more preferably, about 100%) of theaverage microhardness of the abrasive particles prior to such heating.

The thermal stability of certain preferred abrasive particles accordingto the present invention may also be observed using Scanning ElectronMicroscopy (SEM), wherein the average microstructure (e.g., porosity,crystal structure, colony size and crystal size (eutectic crystals, andprimary crystals, if present) and integrity of the abrasive particles isexamined before and after being heated at 1000° C. in air for 4 hours.The microstructure of certain preferred abrasive particles according tothe present invention are essentially the same before and after beingheated at 1000° C. in air for 4 hours.

Further, the thermal stability of certain preferred abrasive particlesaccording to the present invention may also be illustrated by comparingthe color of the abrasive particles before and after they are heated at1000° C. in air for 4 hours. The microstructure of certain preferredabrasive particles according to the present invention is essentially thesame before and after being heated at 1000° C. in air for 4 hours.

The thermal stability of certain preferred abrasive particles accordingto the present invention may also be illustrated by comparing powder XRDresult of the abrasive particles before and after they are heated at1000° C. in air for 4 hours. As discussed above, when alumina-zirconiaeutectic material is heated in air, typically at least a portion of thezirconia undergoes a tetragonal and/or cubic to monoclinic phasetransformation. The effect of this phase transformation is typicallysignificant enough to be observed via powder XRD. By contrast, theeutectic phases of certain preferred abrasive particles according to thepresent invention do not exhibit such phase transformations when heatedto 1000° C. in air, hence no transformation of the eutectic phases willbe observed in the XRD results.

Fused abrasive particles according to the present invention can be usedin conventional abrasive products, such as coated abrasive products,bonded abrasive products (including vitrified, resinoid, and metalbonded grinding wheels, cutoff wheels, mounted points, and honingstones), nonwoven abrasive products, and abrasive brushes. Typically,abrasive products (i.e., abrasive articles) include binder and abrasiveparticles, at least a portion of which is fused abrasive particlesaccording to the present invention, secured within the abrasive productby the binder. Methods of making such abrasive products and usingabrasive products are well known to those skilled in the art.Furthermore, fused abrasive particles according to the present inventioncan be used in abrasive applications that utilize abrasive particles,such as slurries of abrading compounds (e.g., polishing compounds),milling media, shot blast media, vibratory mill media, and the like.

Coated abrasive products generally include a backing, abrasiveparticles, and at least one binder to hold the abrasive particles ontothe backing. The backing can be any suitable material, including cloth,polymeric film, fibre, nonwoven webs, paper, combinations thereof, andtreated versions thereof. The binder can be any suitable binder,including an inorganic or organic binder (including thermally curableresins and radiation curable resins). The abrasive particles can bepresent in one layer or in two layers of the coated abrasive product.

An example of a coated abrasive product is depicted in FIG. 1. Referringto this figure, coated abrasive product 1 has a backing (substrate) 2and abrasive layer 3. Abrasive layer 3 includes fused abrasive particlesaccording to the present invention 4 secured to a major surface ofbacking 2 by make coat 5 and size coat 6. In some instances, a supersizecoat (not shown) is used.

Bonded abrasive products typically include a shaped mass of abrasiveparticles held together by an organic, metallic, or vitrified binder.Such shaped mass can be, for example, in the form of a wheel, such as agrinding wheel or cutoff wheel. The diameter of grinding wheelstypically is about 1 cm to over 1 meter; the diameter of cut off wheelsabout 1 cm to over 80 cm (more typically 3 cm to about 50 cm). The cutoff wheel thickness is typically about 0.5 mm to about 5 cm, moretypically about 0.5 mm to about 2 cm. The shaped mass can also be in theform, for example, of a honing stone, segment, mounted point, disc (e.g.double disc grinder) or other conventional bonded abrasive shape. Bondedabrasive products typically comprise about 3-50% by volume bondmaterial, about 30-90% by volume abrasive particles (or abrasiveparticle blends), up to 50% by volume additives (including grindingaids), and up to 70% by volume pores, based on the total volume of thebonded abrasive product.

A preferred form is a grinding wheel. Referring to FIG. 2, grindingwheel 10 is depicted, which includes fused abrasive particles accordingto the present invention 11, molded in a wheel and mounted on hub 12.

Nonwoven abrasive products typically include an open porous loftypolymer filament structure having fused abrasive particles according tothe present invention distributed throughout the structure andadherently bonded therein by an organic binder. Examples of filamentsinclude polyester fibers, polyamide fibers, and polyaramid fibers. InFIG. 3, a schematic depiction, enlarged about 100×, of a typicalnonwoven abrasive product is provided. Such a nonwoven abrasive productcomprises fibrous mat 50 as a substrate, onto which fused abrasiveparticles according to the present invention 52 are adhered by binder54.

Useful abrasive brushes include those having a plurality of bristlesunitary with a backing (see, e.g., U.S. Pat. No. 5,427,595 (Pihl etal.), U.S. Pat. No. 5,443,906 (Pihl et al.), U.S. Pat. No. 5,679,067(Johnson et al.), and U.S. Pat. No. 5,903,951 (Ionta et al.), thedisclosure of which is incorporated herein by reference). Preferably,such brushes are made by injection molding a mixture of polymer andabrasive particles.

Suitable organic binders for making abrasive products includethermosetting organic polymers. Examples of suitable thermosettingorganic polymers include phenolic resins, urea-formaldehyde resins,melamine-formaldehyde resins, urethane resins, acrylate resins,polyester resins, aminoplast resins having pendant α,β-unsaturatedcarbonyl groups, epoxy resins, acrylated urethane, acrylated epoxies,and combinations thereof. The binder and/or abrasive product may alsoinclude additives such as fibers, lubricants, wetting agents,thixotropic materials, surfactants, pigments, dyes, antistatic agents(e.g., carbon black, vanadium oxide, graphite, etc.), coupling agents(e.g., silanes, titanates, zircoaluminates, etc.), plasticizers,suspending agents, and the like. The amounts of these optional additivesare selected to provide the desired properties. The coupling agents canimprove adhesion to the abrasive particles and/or filler. The binderchemistry may thermally cured, radiation cured or combinations thereof.Additional details on binder chemistry may be found in U.S. Pat. No.4,588,419 (Caul et al.), U.S. Pat. No. 4,751,137 (Tumey et al.), andU.S. Pat. No. 5,436,063 (Follett et al.), the disclosures of which areincorporated herein by reference.

More specifically with regard to vitrified bonded abrasives, vitreousbonding materials, which exhibit an amorphous structure and aretypically hard, are well known in the art. In some cases, the vitreousbonding material includes crystalline phases. Bonded, vitrified abrasiveproducts according to the present invention may be in the shape of awheel (including cut off wheels), honing stone, mounted pointed or otherconventional bonded abrasive shape. A preferred vitrified bondedabrasive product according to the present invention is a grinding wheel.

Examples of metal oxides that are used to form vitreous bondingmaterials include: silica, silicates, alumina, soda, calcia, potassia,titania, iron oxide, zinc oxide, lithium oxide, magnesia, boria,aluminum silicate, borosilicate glass, lithium aluminum silicate,combinations thereof, and the like. Typically, vitreous bondingmaterials can be formed from composition comprising from 10 to 100%glass frit, although more typically the composition comprises 20% to 80%glass frit, or 30% to 70% glass frit. The remaining portion of thevitreous bonding material can be a non-frit material. Alternatively, thevitreous bond may be derived from a non-frit containing composition.Vitreous bonding materials are typically matured at a temperature(s) inthe range from about 700° C. to about 1500° C., usually in the rangefrom about 800° C. to about 1300° C., sometimes in the range from about900° C. to about 1200° C., or even in the range from about 950° C. toabout 1100° C. The actual temperature at which the bond is matureddepends, for example, on the particular bond chemistry.

Preferred vitrified bonding materials may include those comprisingsilica, alumina (preferably, at least 10 percent by weight alumina), andboria (preferably, at least 10 percent by weight boria). In most casesthe vitrified bonding material further comprise alkali metal oxide(s)(e.g., Na₂O and K₂O) (in some cases at least 10 percent by weight alkalimetal oxide(s)).

Binder materials may also contain filler materials or grinding aids,typically in the form of a particulate material. Typically, theparticulate materials are inorganic materials. Examples of usefulfillers for this invention include: metal carbonates (e.g., calciumcarbonate (e.g., chalk, calcite, marl, travertine, marble andlimestone), calcium magnesium carbonate, sodium carbonate, magnesiumcarbonate), silica (e.g., quartz, glass beads, glass bubbles and glassfibers) silicates (e.g., talc, clays, (montmorillonite) feldspar, mica,calcium silicate, calcium metasilicate, sodium aluminosilicate, sodiumsilicate) metal sulfates (e.g., calcium sulfate, barium sulfate, sodiumsulfate, aluminum sodium sulfate, aluminum sulfate), gypsum,vermiculite, wood flour, aluminum trihydrate, carbon black, metal oxides(e.g., calcium oxide (lime), aluminum oxide, titanium dioxide), andmetal sulfites (e.g., calcium sulfite).

In general, the addition of a grinding aid increases the useful life ofthe abrasive product. A grinding aid is a material that has asignificant effect on the chemical and physical processes of abrading,which results in improved performance. Although not wanting to be boundby theory, it is believed that a grinding aid(s) will (a) decrease thefriction between the abrasive particles and the workpiece being abraded,(b) prevent the abrasive particles from “capping” (i.e., prevent metalparticles from becoming welded to the tops of the abrasive particles),or at least reduce the tendency of abrasive particles to cap, (c)decrease the interface temperature between the abrasive particles andthe workpiece, or (d) decreases the grinding forces.

Grinding aids encompass a wide variety of different materials and can beinorganic or organic based. Examples of chemical groups of grinding aidsinclude waxes, organic halide compounds, halide salts and metals andtheir alloys. The organic halide compounds will typically break downduring abrading and release a halogen acid or a gaseous halide compound.Examples of such materials include chlorinated waxes liketetrachloronaphtalene, pentachloronaphthalene, and polyvinyl chloride.Examples of halide salts include sodium chloride, potassium cryolite,sodium cryolite, ammonium cryolite, potassium tetrafluoroboate, sodiumtetrafluoroborate, silicon fluorides, potassium chloride, and magnesiumchloride. Examples of metals include, tin, lead, bismuth, cobalt,antimony, cadmium, and iron titanium. Other miscellaneous grinding aidsinclude sulfur, organic sulfur compounds, graphite, and metallicsulfides. It is also within the scope of the present invention to use acombination of different grinding aids, and in some instances this mayproduce a synergistic effect. The preferred grinding aid is cryolite;the most preferred grinding aid is potassium tetrafluoroborate.

Grinding aids can be particularly useful in coated abrasive and bondedabrasive products. In coated abrasive products, grinding aid istypically used in the supersize coat, which is applied over the surfaceof the abrasive particles. Sometimes, however, the grinding aid is addedto the size coat. Typically, the amount of grinding aid incorporatedinto coated abrasive products are about 50-300 g/m² (preferably, about80-160 g/m²). In vitrified bonded abrasive products grinding aid istypically impregnated into the pores of the product.

The abrasive products can contain 100% fused abrasive particlesaccording to the present invention, or blends of such abrasive particleswith other abrasive particles and/or diluent particles. However, atleast about 2% by weight, preferably at least about 5% by weight, andmore preferably about 30-100% by weight, of the abrasive particles inthe abrasive products should be abrasive particles according to thepresent invention. In some instances, the abrasive particles accordingthe present invention may be blended with another abrasive particlesand/or diluent particles at a ratio between 5 to 75% by weight, about 25to 75% by weight, about 40 to 60% by weight, or about 50% to 50% byweight (i.e., in equal amounts by weight). Examples of suitableconventional abrasive particles include fused aluminum oxide (includingwhite fused alumina, heat-treated aluminum oxide and brown aluminumoxide), silicon carbide, boron carbide, titanium carbide, diamond, cubicboron nitride, garnet, fused alumina-zirconia, and sol-gel-derivedabrasive particles, and the like. The sol-gel-derived abrasive particlesmay be seeded or non-seeded. Likewise, the sol-gel-derived abrasiveparticles may be randomly shaped or have a shape associated with them,such as a rod or a triangle. Examples of sol gel abrasive particlesinclude those described U.S. Pat. No. 4,314,827 (Leitheiser et al.),U.S. Pat. No. 4,518,397 (Leitheiser et al.), U.S. Pat. No. 4,623,364(Cottringer et al.), U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No.4,770,671 (Monroe et al.), U.S. Pat. No. 4,881,951 (Wood et al.), U.S.Pat. No. 5,011,508 (Wald et al.), U.S. Pat. No. 5,090,968 (Pellow), U.S.Pat. No. 5,139,978 (Wood), 5,201,916 (Berg et al.), U.S. Pat. No.5,227,104 (Bauer), U.S. Pat. No. 5,366,523 (Rowenhorst et al.), U.S.Pat. No. 5,429,647 (Larmie), U.S. Pat. No. 5,498,269 (Larmie), and U.S.Pat. No. 5,551,963 (Larmie), the disclosures of which are incorporatedherein by reference. Additional details concerning sintered aluminaabrasive particles made by using alumina powders as a raw materialsource can also be found, for example, in U.S. Pat. No. 5,259,147(Falz), U.S. Pat. No. 5,593,467 (Monroe), and U.S. Pat. No. 5,665,127(Moltgen), the disclosures of which are incorporated herein byreference. In some instances, blends of abrasive particles may result inan abrasive article that exhibits improved grinding performance incomparison with abrasive articles comprising 100% of either type ofabrasive particle.

If there is a blend of abrasive particles, the abrasive particle typesforming the blend may be of the same size. Alternatively, the abrasiveparticle types may be of different particle sizes. For example, thelarger sized abrasive particles may be abrasive particles according tothe present invention, with the smaller sized particles being anotherabrasive particle type. Conversely, for example, the smaller sizedabrasive particles may be abrasive particles according to the presentinvention, with the larger sized particles being another abrasiveparticle type.

Examples of suitable diluent particles include marble, gypsum, flint,silica, iron oxide, aluminum silicate, glass (including glass bubblesand glass beads), alumina bubbles, alumina beads and diluentagglomerates. Fused abrasive particles according to the presentinvention can also be combined in or with abrasive agglomerates.Abrasive agglomerate particles typically comprise a plurality ofabrasive particles, a binder, and optional additives. The binder may beorganic and/or inorganic. Abrasive agglomerates may be randomly shape orhave a predetermined shape associated with them. The shape may be ablock, cylinder, pyramid, coin, square, or the like. Abrasiveagglomerate particles typically have particle sizes ranging from about100 to about 5000 micrometers, typically about 250 to about 2500micrometers. Additional details regarding abrasive agglomerate particlesmay be found, for example, in U.S. Pat. No. 4,311,489 (Kressner), U.S.Pat. No. 4,652,275 (Bloecher et al.), U.S. Pat. No. 4,799,939 (Bloecheret al.), U.S. Pat. No. 5,549,962 (Holmes et al.), and U.S. Pat. No.5,975,988 (Christianson), the disclosures of which are incorporatedherein by reference.

The abrasive particles may be uniformly distributed in the abrasivearticle or concentrated in selected areas or portions of the abrasivearticle. For example, in a coated abrasive, there may be two layers ofabrasive particles. The first layer comprises abrasive particles otherthan abrasive particles according to the present invention, and thesecond (outermost) layer comprises abrasive particles according to thepresent invention. Likewise in a bonded abrasive, there may be twodistinct sections of the grinding wheel. The outermost section maycomprise abrasive particles according to the present invention, whereasthe innermost section does not. Alternatively, abrasive particlesaccording to the present invention may be uniformly distributedthroughout the bonded abrasive article.

Further details regarding coated abrasive products can be found, forexample, in U.S. Pat. No. 4,734,104 (Broberg), U.S. Pat. No. 4,737,163(Larkey), U.S. Pat. No. 5,203,884 (Buchanan et al.), U.S. Pat. No.5,152,917 (Pieper et al.), U.S. Pat. No. 5,378,251 (Culler et al.), U.S.Pat. No. 5,417,726 (Stout et al.), U.S. Pat. No. 5,436,063 (Follett etal.), U.S. Pat. No. 5,496,386 (Broberg et al.), U.S. Pat. No. 5,609,706(Benedict et.al.), U.S. Pat. No. 5,520,711 (Helmin), 5,954,844 (Law etal.), U.S. Pat. No. 5,961,674 (Gagliardi et al.), and U.S. Pat. No.5,975,988 (Christinason), the disclosures of which are incorporatedherein by reference. Further details regarding bonded abrasive productscan be found, for example, in U.S. Pat. No. 4,453,107 (Rue), U.S. Pat.No. 4,741,743 (Narayanan et al.), U.S. Pat. No. 4,800,685 (Haynes etal.), U.S. Pat. No. 4,898,597 (Hay et al.), U.S. Pat. No. 4,997,461(Markhoff-Matheny et al.), U.S. Pat. No. 5,038,453 (Narayanan et al.),U.S. Pat. No. 5,110,332 (Narayanan et al.), and U.S. Pat. No. 5,863,308(Qi et al.) the disclosures of which are incorporated herein byreference. Further, details regarding vitreous bonded abrasives can befound, for example, in U.S. Pat. No. 4,543,107 (Rue), U.S. Pat. No.4,898,597 (Hay), U.S. Pat. No. 4,997,461 (Markhoff-Matheny et al.), U.S.Pat. No. 5,094,672 (Giles et al.), U.S. Pat. No. 5,118,326 (Sheldon etal.), U.S. Pat. No. 5,131,926(Sheldon et al.), U.S. Pat. No. 5,203,886(Sheldon et al.), U.S. Pat. No. 5,282,875 (Wood et al.), U.S. Pat. No.5,738,696 (Wu et al.), and U.S. Pat. No. 5,863,308 (Qi), the disclosuresof which are incorporated herein by reference. Further details regardingnonwoven abrasive products can be found, for example, in U.S. Pat. No.2,958,593 (Hoover et al.), the disclosure of which is incorporatedherein by reference.

Methods for abrading with abrasive particles according to the presentinvention range from snagging (i.e., high pressure high stock removal)to polishing (e.g., polishing medical implants with coated abrasivebelts), wherein the latter is typically done with finer grades (e.g.,less ANSI 220 and finer) of abrasive particles. The abrasive particlemay also be used in precision abrading applications, such as grindingcam shafts with vitrified bonded wheels. The size of the abrasiveparticles used for a particular abrading application will be apparent tothose skilled in the art.

Abrading with abrasive particles according to the present invention maybe done dry or wet. For wet abrading, the liquid may be introducedsupplied in the form of a light mist to complete flood. Examples ofcommonly used liquids include: water, water-soluble oil, organiclubricant, and emulsions. The liquid may serve to reduce the heatassociated with abrading and/or act as a lubricant. The liquid maycontain minor amounts of additives such as bactericide, antifoamingagents, and the like.

Abrasive particles according to the present invention may be used toabrade workpieces such as aluminum metal, carbon steels, mild steels,tool steels, stainless steel, hardened steel, titanium, glass, ceramics,wood, wood like materials, paint, painted surfaces, organic coatedsurfaces and the like. The applied force during abrading typicallyranges from about 1 to about 100 kilograms.

EXAMPLES

This invention is further illustrated by the following examples, but theparticular materials and amounts thereof recited in these examples, aswell as other conditions and details, should not be construed to undulylimit this invention. Various modifications and alterations of thepresent invention will become apparent to those skilled in the art. Allparts and percentages are by weight unless otherwise indicated.

Example 1

A polyethylene bottle was charged with 187.2 grams of alumina powder(obtained under the trade designation “APA-0.5” from Condea Vista,Tucson, Ariz.), 112.9 grams of yttrium oxide powder (obtained from H. C.Starck, Newton, Mass.), 0.6 gram of a dispersing agent (obtained underthe trade designation “DURAMAX D-30005” from Rohm and Haas Company, DearPark, Tex.), and 100.4 grams of distilled water. The powders werepresent in amounts to provide 78.6 mole % Al₂O₃ and 21.4 mole % Y₂O₃.About 450 grams of alumina milling media (10 mm diameter; 99.9% alumina;obtained from Union Process, Akron, Ohio) were added to the bottle, andthe mixture was milled for 4 hours to thoroughly mix the ingredients.After the milling, the milling media were removed and the slurry waspoured onto a glass (“PYREX”) pan where it was dried using a heat-gunheld approximately 46 cm (18 inches) above the pan. The pan was slowlyoscillated while drying to prevent the settling of the powder prior tocomplete drying. After drying with the heat-gun, the pan was placed in adrying oven for an additional 30 minutes at 90° C. to more completelydry the material. The dried powder bed was then scored with a spatulaand scraped from the pan to form small flakes of material. Each flakeweighed about 0.5 to 3 grams. The flakes were calcined in air by heatingthem to 670° C. at rate of about 1° C./min, and then holding them at670° C. for 1 hour, after which the power to the furnace power wasshut-off, and the furnace allowed to cool back to room temperature.

Several of the calcined flakes were melted in an arc discharge furnace(Model No. 1-VAMF-20-22-45; from Advanced Vacuum Systems, Ayer, Mass.).About 15 grams of the calcined flakes were placed on the chilled copperplate located inside a furnace chamber. The furnace chamber wasevacuated and then backfilled with Argon gas at a 260 torr pressure. Anarc was struck between an electrode and a plate. The temperaturesgenerated by the arc discharge were high enough to quickly melt thecalcined flakes. After melting was complete, the material was maintainedin a molten state for about 30 seconds to homogenize the melt. Theresultant melt was rapidly cooled by shutting off the arc and allowingthe melt to cool on its own. Rapid cooling was ensured by small mass ofa sample and a large heat sinking capability of a chilled copper plate.The fused material was removed from the furnace within one minute afterthe power to the furnace was turned off. Although not wanting to bebound by theory, it is estimated that the cooling rate of the melt onthe surface of the water chilled copper plate was 1500° C./min. Thefused material was white-green in color.

FIG. 8 is a scanning electron microscope (SEM) photomicrograph of apolished section of fused Example 1 material. The polished section wasprepared using conventional mounting and polishing techniques. Polishingwas done using a polisher (obtained from Buehler of Lake Bluff, IL underthe trade designation “ECOMET 3 TYPE POLISHER-GRINDER”). The sample waspolished for about 3 minutes with a diamond wheel, followed by threeminutes of polishing with each of 45, 30, 15, 9, and 3 micrometerdiamond slurries. The polished sample was coated with a thin layer ofgold-palladium and viewed using JEOL SEM (Model JSM 840A). Referringagain to FIG. 8, the photomicrograph shows a eutectic-derivedmicrostructure comprising a plurality of colonies. The colonies wereabout 10-40 micrometers in size. Based on powder x-ray diffraction of aportion of Example 1 material, and examination of the polished sampleusing SEM in the backscattered mode, it is believed that the whiteportions in the photomicrograph were crystalline Y₃Al₅O₁₂, and the darkportions (α-Al₂O₃. The widths of these phases observed in the polishedsection were up to about 1 micrometer.

Example 1 fused material was crushed by using a “Chipmunk” jaw crusher(Type VD, manufactured by BICO Inc., Burbank, Calif.) into (abrasive)particles and graded to retain the −25+30 and −30+35 mesh fractions (USAStandard Testing Sieves). These two mesh fractions were combined toprovide a 50/50 blend. Thirty grams of the 50/50 blend of −25+30 and−30+35 mesh fractions were incorporated into a coated abrasive disc. Thecoated abrasive disc was made according to conventional procedures. Thefused abrasive particles were bonded to 17.8 cm diameter, 0.8 mm thickvulcanized fiber backings (having a 2.2 cm diameter center hole) using aconventional calcium carbonate-filled phenolic make resin (48% resolephenolic resin, 52% calcium carbonate, diluted to 81% solids with waterand glycol ether) and a conventional cryolite-filled phenolic size resin(32% resole phenolic resin, 2% iron oxide, 66% cryolite, diluted to 78%solids with water and glycol ether). The wet make resin weight was about185 g/m². Immediately after the make coat was applied, the fusedabrasive particles were electrostatically coated. The make resin wasprecured for 120 minutes at 88° C. Then the cryolite-filled phenolicsize coat was coated over the make coat and abrasive particles. The wetsize weight was about 850 g/m². The size resin was cured for 12 hours at99° C. The coated abrasive disc was flexed prior to testing.

The average microhardnesses of Example 1 abrasive particles weremeasured by mounting loose abrasive particles (about 10 mesh in size) inmounting resin (obtained under the trade designation “EPOMET” fromBuehler Ltd., Lake Bluff, Ill.). The resulting cylinder of resin wasabout 2.5 cm (1 inch) in diameter and about 1.9 cm (0.75 inch) tall. Themounted samples were polished using a conventional grinder/polisher(obtained under the trade designation “EPOMET” from Buehler Ltd.) andconventional diamond slurries with the final polishing step using a 1micrometer diamond slurry (obtained under the trade designation “METADI”from Buehler Ltd.) to obtain polished cross-sections of the sample.

The microhardness measurements were made using a conventionalmicrohardness tester (obtained under the trade designation “MITUTOYOMVK-VL” from Mitutoyo Corporation, Tokyo, Japan) fitted with a Vickersindenter using a 500-gram indent load. The microhardness measurementswere made according to the guidelines stated in ASTM Test Method E384Test Methods for Microhardness of Materials (1991), the disclosure ofwhich is incorporated herein by reference. The microhardness values werean average of 20 measurements. The average microhardness was 16.2 GPa.

Several Example 1 abrasive particles were heated placed in a platinumcrucible and heated to 1000° C. at 50° C./hour, held at 1000° C. for 4hours (in air), and then cooled to room temperature at about 100°C./hour. The color of the abrasive particles after heating was the sameas before heating (i.e., white-green). The average microhardness of theabrasive particles after heating was 16.1 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved after heating was substantially the same as the microstructureobserved before heating.

Several Example 1 abrasive particles were also heated placed in aplatinum crucible and heated to 1000° C. at 50° C./hour, held at 1000°C. for 8 hours (in air), and then cooled to room temperature at about100° C./hour. The color of the abrasive particles after heating was thesame as before heating (i.e., white-green). The average microhardness ofthe abrasive particles after heating was 16.0 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved after heating was substantially the same as the microstructureobserved before heating.

Comparative Example A

The Comparative Example A coated abrasive disc was prepared as describedin Example 1 except heat-treated fused alumina abrasive particles(obtained under the trade designation “ALODUR BFRPL”” from Triebacher,Villach, Austria) was used in place of the Example 1 fused abrasiveparticles.

Comparative Example B

The Comparative Example B coated abrasive disc was prepared as describedin Example 1 except alumina-zirconia abrasive particles (having aeutectic composition of 53% Al₂O₃ and 47% ZrO₂; obtained under the tradedesignation “NORZON” from Norton Company, Worcester, Mass.) was used inplace of the Example 1 fused abrasive particles.

The average microhardness of Comparative Example B abrasive particleswas determined, as described above in Example 1, to be 16.0 GPa. Thecolor of the Comparative Example B abrasive particles was gray-navyblue.

Several Comparative Example B abrasive particles were heated placed in aplatinum crucible and heated to 1000° C. at 50° C./hour, held at 1000°C. for 4 hours (in air), and then cooled to room temperature at about100° C./hour. The color of the abrasive particles after heating wasbeige. The average microhardness of the abrasive particles after heatingwas 12.9 GPa. The polished cross-sections prepared for the microhardnessmeasurements were examined using the SEM in the secondary electron mode.An SEM photomicrograph a Comparative Example B abrasive particle beforeheating is shown in FIG. 11. An SEM photomicrograph a ComparativeExample B abrasive particle after heating is shown in FIG. 12. Themicrostructure observed after heating was different than that observedbefore heating. The differences were observed most predominately at thecolony boundaries.

Further powder x-ray diffraction (using a Phillips XRG 3100 x-raydiffractometer with copper K α1 radiation of 1.54050 Angstrom) was usedto qualitatively measure the phases present in Comparative Example Babrasive particles before and after the above described heat-treatmentby comparing the peak intensities of 111 of cubic and/or tetragonalreflection at about 2θ=30 degrees, to that of 11{overscore (1)} ofmonoclinic reflection at about 2θ=28 degrees. For reference see “PhaseAnalysis in Zirconia Systems,” Garvie, R. C. and Nicholson, P. S.,Journal of the American Ceramic Society, vol 55 (6), pp. 303-305, 1972,the disclosure of which is incorporated herein by reference. The sampleswere ground and −120 mesh powders used for analysis. The unheat-treatedComparative Example B abrasive particles contained both the monoclinicand cubic and/or tetragonal zirconia phases. For the heat-treatedsample, a decrease in the cubic and/or tetragonal phase content with acorresponding increase in monoclinic phase content was observed.

Several Comparative Example B abrasive particles were heated placed in aplatinum crucible and heated to 1000° C. at 50° C./hour, held at 1000°C. for 8 hours (in air), and then cooled to room temperature at about100° C./hour. The color of the abrasive particles after heating wasbeige. The average microhardness of the abrasive particles after heatingwas 12.8 GPa. The polished cross-sections prepared for the microhardnessmeasurements were examined using the SEM in the secondary electron mode.An SEM photomicrograph a Comparative Example B abrasive particle afterheating is shown in FIG. 13. The microstructure observed after heatingwas different than that observed before heating. The differences, whichwere greater than those observed for the heat-treatment at 1000° C. for4 hours, were again observed most predominately at the colonyboundaries.

The effect of two vitrified bonding materials on Comparative Example Babrasive particles were evaluated as follows. A first vitrified bondmaterial was prepared by charging a plastic jar (4 3/8 inches (11.1 cm)in diameter; 4 ⅜ inches (11.1 cm) in height) with 70 parts of a glassfrit (37.9% SiO₂, 28.5%B₂O₃, 15.6% Al₂O₃, 13.9% Na₂O, and 4.1% K₂O;obtained under the trade designation “FERRO FRIT 3227” from FerroCorporation, Cleveland, Ohio), 27 parts of Kentucky Ball Clay (No 6DC;obtained from Old Hickory Clay Company, Hickory, Ky.), 3.5 parts ofLi₂CO₃ (obtained from Alfa Aesar Chemical Company, Ward Hill, Mass.), 3parts CaSiO₃ (obtained from Alfa Aesar Chemical Company), and 625 gramsof 1.3 cm (0.5 inch) diameter plastic coated steel media, and then drymilling the contents at 90 rpm for 7 hours. The composition wasformulated to provide a vitrified bond material comprising about 45%SiO₂, about 19% Al₂O₃, about 20% B₂O₃, about 10% Na₂O, about 3% K₂O,about 1.5% Li₂O, and about 1.5% CaO. The dry milled material andComparative Example B abrasive particles were pressed into a 3.2 cm×0.6cm (1.25 inch×0.25 inch) pellet. The pellet was heated to 1000° C. at50° C./hour, held at 1000° C. for 8 hours (in air), and then cooled toroom temperature at about 100° C./hour. The pellet was prepared bymixing, in order, 20 parts of Comparative Example B abrasive particles(−20+30 mesh), 0.24 part of hydrolyzed starch (obtained under the tradedesignation “DEXTRIN” from Aldrich Chemical Company, Milwaukee, Wis.),0.02 part glycerine (obtained from Aldrich Chemical Company), 0.72 partwater, 3.14 parts of the dry milled material, and 0.4 part of hydrolyzedstarch (“DEXTRIN”). The pellet was pressed under a load of 2273kilograms (5000 lbs.). The average microhardness of the abrasiveparticles after heating in the vitrified bonding material was 13.6 GPa,although some of the Comparative Example B abrasive particles exhibitsuch severe degradation that microhardness measurements could not beeffectively made (portions of the particles were too weak). There wasvariability in the color of the heat-treated abrasive particles,although the majority of the particles were beige. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. An SEM photomicrograph aComparative Example B abrasive particle after heating is shown in FIG.14. The microstructure observed after heating was different than thatobserved before heating. The differences, which were greater than thoseobserved for the heat-treatment at 1000° C. for 4 hours, were againobserved most predominately at the colony boundaries.

A second vitrified bond material was prepared by charging a plastic jar(4 ⅜ inches (11.1 cm) in diameter; 4 ⅜ inches (11.1 cm) in height) with45 parts of Kentucky Ball Clay (No. 6DC; obtained from Old Hickory ClayCompany), 28 parts of anhydrous sodium tetraborate (obtained from AlfaAesar Chemical Company), 25 parts of feldspar (obtained under the tradedesignation “G-200 Feldspar” from Feldspar Corporation, Atlanta, Ga.),3.5 parts of Li₂CO₃ (obtained from Alfa Aesar Chemical Company), 2.5parts of CaSiO₃ (obtained from Alfa Aesar Chemical Company), and 625grams of 1.3 cm (0.5 inch) diameter plastic coated steel media, and thendry milling the contents at 90 rpm for 7 hours. The composition wasformulated to provide a vitrified bond material comprising about 45%SiO₂, about 19% Al₂O₃, about 20% B₂O₃, about 10% Na₂O, about 3% K₂0,about 1.5% Li₂O, and about 1.5% CaO. The dry milled material andComparative Example B abrasive particles were pressed into a 3.2 cm×0.6cm (1.25 inch×0.25 inch) pellet. The pellet was heated to 1000° C. at50° C./hour, held at 1000° C. for 8 hours (in air), and then cooled toroom temperature at about 100° C./hour. The pellet was prepared bymixing, in order, 20 parts of Comparative Example B abrasive particles(−20+30 mesh), 0.24 part of hydrolyzed starch (“DEXTRIN”), 0.02 partglycerine (obtained from Aldrich Chemical Company), 0.72 part water,3.14 parts of the dry milled material, and 0.4 part of hydrolyzed starch(“DEXTRIN”). The pellet was pressed under a load of 2273 kilograms (5000lbs.). The average microhardness of the abrasive particles after heatingin the vitrified bonding material was 13.4 GPa, although some of theComparative Example B abrasive particles exhibit such severe degradationthat microhardness measurements could not be effectively made (portionsof the particles were too weak). There was variability in the color ofthe heat-treated abrasive particles, although the majority of theparticles were beige. The polished cross-sections prepared for themicrohardness measurements were examined using the SEM in the secondaryelectron mode. The microstructure observed after heating was differentthan that observed before heating. The differences, which were greaterthan those observed for the heat-treatment at 1000° C. for 4 hours, wereagain observed most predominately at the colony boundaries.

Comparative Example C

The Comparative Example C coated abrasive disc was prepared as describedin Example 1 except sol-gel-derived abrasive particles (commerciallyavailable under the trade designation “321 CUBITRON” from the 3MCompany, St. Paul, Minn.) was used in place of the Example 1 fusedabrasive particles.

Grinding Performance of Example 1 and Comparative Exales A-C

The grinding performance of Example 1 and Comparative Examples A-Ccoated abrasive discs were evaluated as follows. Each coated abrasivedisc was mounted on a beveled aluminum back-up pad, and used to grindthe face of a pre-weighed 1.25 cm×18 cm×10 cm 1018 mild steel workpiece.The disc was driven at 5,000 rpm while the portion of the discoverlaying the beveled edge of the back-up pad contacted the workpieceat a load of 8.6 kilograms. Each disc was used to grind individualworkpiece in sequence for one-minute intervals. The total cut was thesum of the amount of material removed from the workpieces throughout thetest period. The total cut by each sample after 12 minutes of grindingas well as the cut at 12th minute (i.e., the final cut) are reported inTable 1, below.

TABLE 1 Example Total cut, g Final cut, g Comp. A 418 23 Comp. B 621 48Comp. C 859 75 1 732 56

Example 2

Example 2 fused material and abrasive particles were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 173 grams of alumina powder (“APA-0.5”), 19.3 grams of magnesiumoxide powder (obtained under the trade designation “MAGCHEM 10-325” fromMartin Marietta Magnesia Specialties, Hunt Valley, Md.), 107.8 grains ofyttrium oxide powder obtained from H. C. Starck, Newton, Mass.), 0.6gram of a dispersing agent (“DURAMAX D-30005”), and 137.4 grams ofdistilled water, and (b) the powders were present in amounts to provide64 mole % Al₂O₃, 18 mole % MgO, and 18 mole % Y₂O₃. The fulsed materialwas white in color.

FIG. 9 is a scanning electron microscope (SEM) photornicrograph of apolished section (prepared as described in Example 1) of fused Example 2material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies are about 10-40micrometers in size. Based on powder x-ray diffraction of a portion ofExample 2 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline Y₃Al₅O₁₂, and the dark portions acrystalline Al₂O₃-rich spinel solid solution phase. The width of thesephases observed in the polished section were up to about 1 micrometer.

Comparative Example D

Comparative Example D fused material and abrasive particles wereprepared as described in Example 1, except (a) the polyethylene bottlewas charged with 149.5 grams of alumina powder (“APA-0.5”), 149.4 grainsof yttria-stabilized zirconia oxide powder (with a nominal compositionof 94 wt % ZrO₂ (+HfO₂) and 5.4 wt % Y₂O₃; obtained under the tradedesignation “HSY 3.0” from Zirconia Sales, Inc. of Marietta, Ga.), 0.6gram of a dispersing agent (“DURAMAX D-30005”), and 136.5 grams ofdistilled water, and (b) the powders were present in amounts to provide54.8 mole % Al₂O₃ and 45.2 mole % ZrO₂. The fused material was white incolor.

FIG. 10 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fusedComparative Example D material. The photomicrograph shows a eutecticderived microstructure comprising a plurality of colonies. The colonieswere about 5-40 micrometers in size. Based on powder x-ray diffractionof a portion of Comparative Example D material, and examination of thepolished sample using SEM in the backscattered mode, it is believed thatthe white portions in the photomicrograph were crystalline ZrO₂, and thedark portions α-Al₂O₃. The widths of these phases observed in thepolished section were up to about 0.5 micrometer.

The average microhardness of Comparative Example D was determined, asdescribed above in Example 1, to be 15.3 GPa.

Several Comparative Example D particles were heated placed in a platinumcrucible and heated to 1000° C. at 50° C./hour, held at 1000° C. for 4hours (in air), and then cooled to room temperature at about 100°C./hour. The color of the abrasive particles after heating was white.The average microhardness of the abrasive particles after heating was15.0 GPa. The polished cross-sections prepared for the microhardnessmeasurements were examined using the SEM in the secondary electron mode.An SEM photomicrograph Comparative Example D material before heating isshown in FIG. 15. The microstructure observed after heating wassubstantially the same as the microstructure observed before heating.

Further powder x-ray diffraction, as described above for ComparativeExample B, was used to qualitatively measure the phases present inComparative Example D material before and after the above describedheat-treatment by comparing the peak intensities of 111 of cubic and/ortetragonal reflection at about 2θ=30 degrees, to that of 11{overscore(1)} of monoclinic reflection at about 2θ=28 degrees. The unheat-treatedComparative Example D material contained predominantly cubic and/ortetragonal zirconia before and after the heat-treatment (i.e., there wasno significant difference noted in the x-ray diffraction results).

Several Comparative Example D particles were also heated placed in aplatinum crucible and heated to 1000° C. at 50° C./hour, held at 1000°C. for 8 hours (in air), and then cooled to room temperature at about100° C./hour. The color of the abrasive particles after heating waswhite. The average microhardness of the abrasive particles after heatingwas 15.0 GPa. The polished cross-sections prepared for the microhardnessmeasurements were examined using the SEM in the secondary electron mode.The microstructure observed after heating was only slightly differentthan that observed before heating. An SEM photomicrograph ComparativeExample D after heating is shown in FIG. 16. There was some cracksobserved in the heat-treated material, generally near primary crystalsof ZrO₂.

Differential Thermal Analysis (DTA) And Thermogravimetric Analysis (TGA)of Example 1 and Comparative Example B and D AbrasiveParticles/Materials

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA)were conducted for each of Example 1 and Comparative Example B and Dabrasive particles/materials. Each material was crushed with a mortarand pestle and screened to retain particles that were in the 400-500micrometer size range.

DTA/TGA runs were made (using an instrument obtained from NetzschInstruments, Selb, Germany under the trade designation “NETZSCH STA 409DTA/TGA”) for each of the screened samples. The amount of each screenedsample placed in the 100 microliter Al₂O₃ sample holder was 129.5micrograms (Example 1), 125.8 micrograms (Comparative Example D), 127.3micrograms (Comparative Example B), respectively. Each sample was heatedin static air at a rate of 10° C./minute from room temperature (about25° C.) to 1300° C.

Referring to FIG. 5, line 157 is the plotted DTA data for the Example 1material; line 159, the plotted TGA data. Referring to FIG. 6, line 177is the plotted DTA data for the Comparative Example D material; line179, the plotted TGA data. Referring to FIG. 7, line 187 is the plottedDTA data for the Comparative Example B material; line 189, the plottedTGA data. The change in weight of the sample through the TGA run was,for Example 1, 0.22%; for Comparative Example D, 0.73%; and, forComparative Example B, 1.16%.

Example 3

Example 3 fused material was prepared as described in Example 1, except(a) the polyethylene bottle was charged with 201.9 grams of aluminapowder (“APA-0.5”) and 98.1 grams of yttrium oxide powder (obtained fromH. C. Starck, Newton, Mass.), and (b) the powders were present inamounts to provide 82 mole % Al₂O₃ and 18 mole % Y₂O₃.

FIG. 27 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 3material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 10-40micrometers in size. Based on powder x-ray diffraction of a portion ofExample 3 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline Y₃Al₅O₁₂, and the dark portionsα-Al₂O₃. The widths of these phases observed in the polished sectionwere up to about 1 micrometer.

Grinding Performance of Example 3 and Comparative Examples A-C

The grinding performance of Example 3 and Comparative Examples A-Ccoated abrasive discs were evaluated as described above for Example 1and Comparative Examples A-C. The results are reported in Table 2,below.

TABLE 2 Example Total cut, g Final cut, g Comp. A 431 25 Comp. B 674 50Comp. C 933 78 3 787 56

Example 4

Example 4 fused material, abrasive particles, and discs were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 242.5 hgrams of alumina powder (“APA-0.5”), 257.5 grams ofgadolinium oxide powder (obtained from Molycorp, Inc., Brea, Calif.),0.6 gram of a dispersing agent (“DURAMAX D-30005”), and 150.6 grams ofdistilled water, and the powders were present in amounts to provide 77mole % Al₂O₃ and 23 mole % Gd₂O₃. The fused material was white-yellow incolor.

FIG. 17 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 4material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 5-20micrometers in size. Based on powder x-ray diffraction of a portion ofExample 4 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline GdAlO₃, and the dark portions (α-Al₂O₃.The widths of these phases observed in the polished section were up toabout 0.7 micrometer. It is also noted that there were many poresobserved in the fused material.

Example 5

Example 5 fused material, abrasive particles, and discs were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 145.6 grams of alumina powder (“APA-0.5”), 151.2 grams of lanthanumoxide powder (obtained from Molycorp, Inc., Brea, Calif.), 0.6 gram of adispersing agent (“DURAMAX D-30005”), and 129.5 grams of distilledwater, and (b) the powders were present in amounts to provide 75 mole %Al₂O₃ and 25 mole % La₂O₃. The fused material was white-red in color;although some of the abrasive particles were redder than others.

FIG. 18 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 5material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 5-30micrometers in size. Based on powder x-ray diffraction of a portion ofExample 5 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline LaAlO₃, and the dark portionscrystalline LaAl₁₁O₁₈. The widths of these phases observed in thepolished section were up to about 0.5 micrometer. Further, large primarycrystals (believed to be LaAlO₃), present in the form of dendrites, wereobserved in some areas of the polished cross-section, indicatingpossible deviation of the composition from an exact eutectic compositiontoward a La₂O₃ rich composition.

The average microhardness of Example 5 abrasive particles wasdetermined, as described above in Example 1, except Example 5, 6, and 7abrasive particles (i.e., Example 5, 6, and 7 abrasive particles weremixed together; but were distinguishable from each other visually basedon color, and under SEM based on composition) were incorporated into thepellet. The average microhardness of Example 5 abrasive particles was15.0 GPa.

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA)were conducted for Example 5 material as described for Example 1 andComparative Example B and D abrasive particles/materials. Referring toFIG. 19, line 167 is the plotted DTA data for the Example 5 material;line 169, the plotted TGA data. The change in weight of the samplethrough the TGA run was 0.22%. Several Example abrasive particles(together with Examples 6 and 7 abrasive particles) were heated placedin a platinum crucible and heated to 1000° C. at 50° C./hour, held at1000° C. for 4 hours (in air), and then cooled to room temperature atabout 100° C./hour. The color of the Example 5 abrasive particles afterheating was the same as before heating (i.e., white-red). The averagemicrohardness of the Example 5 abrasive particles after heating was 14.1GPa. The polished cross-sections prepared for the microhardnessmeasurements were examined using the SEM in the secondary electron mode.The microstructure observed for the Example 5 abrasive particles afterheating was substantially the same as the microstructure observed beforeheating.

Several Example 5 abrasive particles (together with Example 6 and 7abrasive particles) were also heated placed in a platinum crucible andheated to 1000° C. at 50° C./hour, held at 1000° C. for 8 hours (inair), and then cooled to room temperature at about 100° C./hour. Thecolor of the Example 5 abrasive particles after heating was the same asbefore heating (i.e., white-red). The average microhardness of theExample 5 abrasive particles after heating was 14.3 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved for the Example 5 abrasive particles after heating wassubstantially the same as the microstructure observed before heating.

The effect of two vitrified bonding materials on Example 5 abrasiveparticles were evaluated as described in Comparative Example B, exceptExamples 5, 6, and 7 abrasive particles (i.e., Examples 5, 6, and 7abrasive particles were mixed together; but were distinguishable fromeach other visually based on color, and under SEM based on composition)were incorporated into the pellets. The polished cross-sections wereexamined using the SEM in the secondary electron mode. Themicrostructure observed after heating was substantially the same as themicrostructure observed before heating. The color of the Example 5abrasive particles after heating with the vitrified bonding material wasthe same as before heating (i.e., white-red).

Example 6

Example 6 fused material, abrasive particles, and discs were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 143.6 grams of alumina powder (“APA-0.5”), 147.6 grams of neodymiumoxide powder (obtained from Molycorp, Inc., Brea, Calif.), 0.6 gram of adispersing agent (“DURAMAX D-30005”), and 138.5 grams of distilledwater, and (b) the powders were present in amounts to provide 75 mole %Al₂O₃ and 25 mole % Nd₂O₃. The fused material was white-blue in color;although some of the abrasive particles were bluer than others.

FIG. 20 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 6material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 10-40micrometers in size. Based on powder x-ray diffraction of a portion ofExample 6 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline NdAlO₃, and the dark portionscrystalline NdAl₁₁O₁₈. The widths of these phases observed in thepolished section were up to about 0.5 micrometer. Further, large primarycrystals (believed to be NdAlO₃), present in the form of dendrites, wereobserved in some areas of the polished cross-section, indicatingpossible deviation of the composition from an exact eutectic compositiontoward a Nd₂O₃ rich composition.

The average microhardness of Example 6 was determined, as describedabove in Example 1 except Examples 5, 6, and 7 abrasive particles (i.e.,Examples 5, 6, and 7 abrasive particles were mixed together; but weredistinguishable from each other visually based on color, and under SEMbased on composition) were incorporated into the pellet. The averagemicrohardness of Example 6 abrasive particles was to be 14.5 GPa.

Several Example 6 abrasive particles (together with Examples 5 and 7abrasive particles) were heated placed in a platinum crucible and heatedto 1000° C. at 50° C./hour, held at 1000° C. for 4 hours (in air), andthen cooled to room temperature at about 100° C./hour. The color of theExample 6 abrasive particles after heating was the same as beforeheating (i.e., white-blue). The average microhardness of the Example 6abrasive particles after heating was 14.1 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved for the Example 6 abrasive particles after heating wassubstantially the same as the microstructure observed before heating.

Several Example 6 abrasive particles (together with Examples 5 and 7abrasive particles) were also heated placed in a platinum crucible andheated to 1000° C. at 50° C./hour, held at 1000° C. for 8 hours (inair), and then cooled to room temperature at about 100° C./hour. Thecolor of the Example 6 abrasive particles after heating was the same asbefore heating (i.e., white-blue). The average microhardness of theExample 6 abrasive particles after heating was 14.5 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved for the Example 6 abrasive particles after heating wassubstantially the same as the microstructure observed before heating.

The effect of two vitrified bonding materials on Example 6 abrasiveparticles were evaluated as described in Comparative Example B, exceptExamples 5, 6, and 7 abrasive particles (i.e., Examples 5, 6, and 7abrasive particles were mixed together; but were distinguishable fromeach other visually based on color, and under SEM based on composition)were incorporated into the pellets. The polished cross-sections wereexamined using the SEM in the secondary electron mode. Themicrostructure observed after heating was substantially the same as themicrostructure observed before heating. The color of the Example 6abrasive particles after heating with the vitrified bonding material wasthe same as before heating (i.e., white-blue).

Example 7

A lanthanum carbonate powder (obtained from Aptech Services, LLC,Houston, Tex.; Lot No.: SH99-5-7) was heated to 900° C. to convert it tolanthanum oxide and some cerium (IV) oxide (manufacturer's conversionspecifications were 95% La₂O₃ and 4.19% CeO₂, with a carbonate to oxideyield of 49.85 wt. % metal oxide). Example 7 fused material, abrasiveparticles, and discs were prepared as described in Example 1, except (a)the polyethylene bottle was charged with 148.6 grams of thelanthanum/cerium oxide powder, 146.4 grams of alumina powder(“APA-0.5”), 0.6 gram of a dispersing agent (“DURAMAX D-30005”) and141.3 grams of distilled 10 water, and (b) the powders were present inamounts to provide 75 mole % Al₂O₃ and 25 mole % La₂O₃/Ce₂O₃. It wasobserved that the slurry was significantly more viscous as compared tothe slurry of Example 5. The fused material was bright orange in color.

FIG. 21 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 7material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 5-25micrometers in size. Based on powder x-ray diffraction of a portion ofExample 7 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline LaAlO₃, and the dark portionscrystalline LaAl₁₁O₁₈. The widths of these phases observed in thepolished section were up to about 0.5 micrometer. Further, large primarycrystals (believed to be LaAlO₃), present in the form of dendrites, wereobserved in some areas of the polished cross-section, indicatingpossible deviation of the composition from an exact eutectic compositiontoward a La₂O₃ rich composition.

The average microhardness of Example 7 abrasive particles wasdetermined, as described above in Example 1, except Examples 5, 6, and 7abrasive particles (i.e., Examples 5, 6, and 7 abrasive particles weremixed together; but were distinguishable from each other visually basedon color, and under SEM based on composition) were incorporated into thepellet. The average microhardness of Example 7 abrasive particles was14.8 GPa.

Several Example 7 abrasive particles (together with Examples 5 and 6abrasive particles) were heated placed in a platinum crucible and heatedto 1000° C. at 50° C./hour, held at 1000° C. for 4 hours (in air), andthen cooled to room temperature at about 100° C./hour. The color of theExample 7 abrasive particles after heating was the same as beforeheating (i.e., bright orange). The average microhardness of the Example7 abrasive particles after heating was 14.7 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved for the Example 7 abrasive particles after heating wassubstantially the same as the microstructure observed before heating.

Several Example 7 abrasive particles (together with Example 5 and 6abrasive particles) were also heated placed in a platinum crucible andheated to 1000° C. at 50° C./hour, held at 1000° C. for 8 hours (inair), and then cooled to room temperature at about 100° C./hour. Thecolor of the Example 7 abrasive particles after heating was the same asbefore heating (i.e., bright orange). The average microhardness of theExample 7 abrasive particles after heating was 14.1 GPa. The polishedcross-sections prepared for the microhardness measurements were examinedusing the SEM in the secondary electron mode. The microstructureobserved for the Example 7 abrasive particles after heating wassubstantially the same as the microstructure observed before heating.

The effect of two vitrified bonding materials on Example 7 abrasiveparticles were evaluated as described in Comparative Example B, exceptExamples 5, 6, and 7 abrasive particles (i.e., Example 5, 6, and 7abrasive particles were mixed together; but were distinguishable fromeach other visually based on color, and under SEM based on composition)were incorporated into the pellets. The polished cross-sections wereexamined using the SEM in the secondary electron mode. Themicrostructure observed after heating was substantially the same as themicrostructure observed before heating. The average microhardness of theExample 7 abrasive particles after heating in the two vitrified bondingmaterials was 14.2 GPa and 14.3 GPa, respectively. The color of theExample 7 abrasive particles after heating with each of the twovitrified bonding materials was the same as before heating (i.e., brightorange).

Grinding Performance of Examples 4-7 and Comparative Examples A-C

The grinding performance of Examples 4-7 and Comparative Examples A-Ccoated abrasive discs were evaluated as described for Example 1 andComparative Examples A-C. The results are reported in Table 3, below.

TABLE 3 Example Total cut, g Final cut, g Comp. A 418 23 Comp. B 621 48Comp. C 859 75 4 732 56 5 585 41 6 603 37 7 564 34

Example 8

Example 8 fused material and abrasive particles were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 144.5 grams of alumina powder (“APA-0.5”), 147.4 grams of cerium(IV) oxide (CeO₂) powder, (obtained from Aldrich Chemical Company, Inc.,Milwaukee, Wis.), 0.6 gram of a dispersing agent (“DURAMAX D-30005”),and 137.5 grams of distilled water, (b) the powders were present inamounts to provide 75 mole % Al₂O₃ and 25 mole % Ce₂O₃. The fusedmaterial was intense yellow-green in color.

FIG. 22 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 8material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 5-30micrometers in size. Based on powder x-ray diffraction of a portion ofExample 8 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline CeAlO₃ and crystalline CeO₂, and thedark portions crystalline CeAl₁₁O₁₈. The widths of these phases observedin the polished section were up to about 0.5 micrometer. Further, largeprimary crystals (believed to be CeAlO₃ and/or CeO₂), present in theform of dendrites, were observed in some areas of the polishedcross-section, indicating possible deviation of the composition from anexact eutectic composition toward a CeAlO₃ and/or CeO₂ rich composition.

Example 9

Example 9 fused material and abrasive particles were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 146.5 grams of alumina powder (“APA-0.5”), 147.4 grams ofdysprosium oxide powder (obtained from Aldrich Chemical Company, Inc.,Milwaukee, Wis.), 0.6 gram of a dispersing agent (“DURAMAX D-30005”),and 136.3 grams of distilled water, and (b) the powders were present inamounts to provide 78 mole % Al₂O₃ and 22 mole % Dy₂O₃. The fusedmaterial was white in color.

FIG. 23 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example 9material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 5-20micrometers in size. Based on powder x-ray diffraction of a portion ofExample 9 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline Dy₃Al₅O₁₂, and the dark portionsα-Al₂O₃. The widths of these phases observed in the polished sectionwere up to about 1 micrometer. Primary crystals were not observed.

Example 10

Example 10 fused material and abrasive particles were prepared asdescribed in Example 1, except (a) the polyethylene bottle was chargedwith 146.3 grams of alumina powder (“APA-0.5”), 148.4 grams of ytterbiumoxide powder (obtained from Aldrich Chemical Company, Inc.), 0.6 gram ofa dispersing agent “DURAMAX D-30005”), and 139.6 grams of distilledwater, (b) the powders were resent in amounts to provide 78.6 mole %Al₂O₃ and 21.4 mole % Yb₂O₃. The fused aterial was gray in color.

FIG. 24 is a scanning electron microscope (SEM) photomicrograph of aolished section (prepared as described in Example 1) of fused Example 10material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies are about 5-25micrometers in size. Based on powder x-ray diffraction of a portion ofExample 10 material, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline Yb₃Al₅O₁₂, and the dark portionsα-Al₂O₃. The width of these phases observed in the polished section wereup to about 1 micrometer. Further, large primary crystals (believed tobe α-Al₂O₃), present in the form of dendrites, were observed in someareas of the polished cross-section, indicating possible deviation ofthe composition from an exact eutectic composition toward an Al₂O₃ richcomposition.

Example 11

Example 11 fused material, abrasive particles, and discs were preparedas described in Example 1, except (a) the polyethylene bottle wascharged with 155.6 grams of alumina powder (“APA-0.5”), 144.3 grams oflanthanum oxide powder (obtained from Molycorp, Inc., Brea, Calif.), 0.6gram of a dispersing agent (“DURAMAX D-30005”), and 130 grams ofdistilled water, and (b) the powders were present in amounts to provide77.5 mole % Al₂O₃ and 22.5 mole % La₂O₃. The fused material waswhite-red in color; although some of the abrasive particles were redderthan others.

FIG. 25 is a scanning electron microscope (SEM) photomicrograph of apolished section (prepared as described in Example 1) of fused Example11 material. The photomicrograph shows a eutectic-derived microstructurecomprising a plurality of colonies. The colonies were about 5-30micrometers in size. Based on powder x-ray diffraction of a portion ofExample 1 Imaterial, and examination of the polished sample using SEM inthe backscattered mode, it is believed that the white portions in thephotomicrograph were crystalline LaAlO₃, and the dark portionscrystalline LaAl₁₁O₁₈. The widths of these phases observed in thepolished section were up to about 0.5 micrometer. Further, large primarycrystals (believed to be LaAlO₃), present in the form of dendrites, wereobserved in some areas of the polished cross-section, indicatingpossible deviation of the composition from an exact eutectic compositiontoward a La₂O₃ rich composition.

The grinding performance of Example 11 and Comparative Examples A-Ccoated abrasive discs were evaluated as described above for Example 1and Comparative Examples A-C. The results are reported in Table 4,below.

TABLE 4 Example Total cut, g Final cut, g Comp. A 404 21 Comp. B 647 51Comp. C 952 79 11 690 52

Example 12

Example 12 fused material was prepared as described in Example 1, exceptthe polyethylene bottle was charged with 132.3 grams of alumina powder(“APA-0.5”), 122.7 grams of lanthanum oxide powder (obtained fromMolycorp. Inc., Brea Calif.), 45 grams of aluminum nitride powder (TypeF obtained from Tokuyama Soda Co.) and 150 grams of isopropyl alcohol.

FIG. 26 is an SEM photomicrograph of a polished section (prepared asdescribed in Example 1) of fused Example 12 material. Thephotomicrograph shows a eutectic-derived microstructure comprising aplurality of colonies. The colonies were about 5-30 micrometers in size.The orientation and morphology of crystals making up the colonies variedfrom one colony to another. Based on powder x-ray diffraction of aportion of Example 12 material, and examination of the polished sampleusing SEM in the backscattered mode, it is believed that the whiteportions in the photomicrograph were crystalline LaAlO₃ and the darkportions LaAl₁₁O₁₈. FIG. 26 also shows the presence of a third phase inthe form of largely spherical inclusions. These inclusions are believedto be AlN phase. The widths of crystals of LaAlO₃ and LaAl₁₁O₁₈ phasesobserved in the polished section were up to about 1 micrometer.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. A plurality of abrasive particles having aspecified nominal grade, said plurality of abrasive particle having aparticle size distribution ranging from fine to coarse, wherein at leasta portion of said abrasive particles is a plurality of fused,crystalline abrasive particles, said fused abrasive particles comprisingat least 20 percent by volume, based on the total metal oxide volume ofthe respective particle, eutectic colonies, said colonies comprising athree-dimensional, interpenetrating network of first and secondcrystalline metal oxide phases, said first phase comprising at least oneof crystalline Al₂O₃ or a first, crystalline complex Al₂O₃.metal oxideand said second phase comprising a second, different crystalline complexAl₂O₃.metal oxide.
 2. The plurality of abrasive particles according toclaim 1 wherein said fused, crystalline abrasive particles comprise atleast 50 percent by volume, based on the total metal oxide volume of therespective particle, of said eutectic colonies.
 3. The plurality ofabrasive particles according to claim 2 comprising, on a theoreticaloxide basis, at least 40 percent by weight Al₂O₃, based on the totalmetal oxide content of the respective particle.
 4. The plurality ofabrasive particles according to claim 3, wherein said first crystallinemetal oxide phase is crystalline Al₂O₃.
 5. The plurality of abrasiveparticles according to claim 3, wherein said first crystalline metaloxide phase is said first, crystalline complex Al₂O₃.metal oxide.
 6. Theplurality of abrasive particles according to claim 3, wherein said firstcrystalline metal oxide phase is crystalline Al₂O₃, and wherein saidsecond crystalline metal oxide phase is Y₃Al₅O₁₂.
 7. The plurality ofabrasive particles according to claim 3, wherein said first crystallinemetal oxide phase is crystalline Al₂O₃, and wherein said secondcrystalline metal oxide phase is selected from the group consisting ofDy₃Al₅O₁₂, Er₃Al₅O₁₂, GdAlO₃, and Yb₃Al₅O₁₂.
 8. The plurality ofabrasive particles according to claim 3, wherein said first crystallinemetal oxide phase is selected from the group consisting crystallineCeAlO₃, EuAlO₃, LaAlO₃, NdAlO₃, PrAlO₃, and SmAlO₃, and wherein saidsecond crystalline metal oxide phase is crystalline CeAl₁₁O₁₈,EuAl₁₁O₁₈, LaAl₁₁O₁₈, NdAl₁₁O₁₈, PrAl₁₁O₁₈, and SmAl₁₁O₁₈, respectively.9. The plurality of abrasive particles according to claim 3, whereinsaid eutectic colonies have an average size of less than 100micrometers.
 10. The plurality of abrasive particles according to claim3, wherein said eutectic colonies have an average size of less than 50micrometers.
 11. The plurality of abrasive particles according to claim3, wherein said fused, crystalline abrasive particles have an averagemicrohardness of at least 13 GPa.
 12. A method for by for used,crystalline abrasive particles comprising at least 20 percent by volume,based on the total metal oxide volume of the respective particle,eutectic colonies, said colonies comprising a three-dimensional,interpenetrating network of first and second crystalline metal oxidephases, said first phase comprising at least one of crystalline Al₂O₃ ora first, crystalline complex Al₂O₃.metal oxide and said second phasecomprising a second, different crystalline complex Al₂O₃.metal oxide,said method comprising: melting at least one Al₂O₃ source and at leastone reactive Al₂O₃ metal oxide source to provide a melt; converting themelt to said fused, crystalline abrasive particles; and grading saidfused, crystalline abrasive particles to provide a plurality of abrasiveparticles having a specified nominal grade, said plurality of abrasiveparticles having a particle size distribution ranging from fine tocoarse, wherein at least a portion of said plurality of abrasiveparticles is a plurality of said fused, crystalline abrasive particles.13. The method according to claim 12, wherein converting includes:cooling the melt to provide a solidified material; and crushing thesolidified material to provide said fused, crystalline abrasiveparticles.
 14. The method according to claim 13, wherein cooling themelt includes cooling the melt with metallic plates.
 15. The methodaccording to claim 13, wherein cooling the melt includes cooling themelt with metallic balls.
 16. An abrasive article comprising a binderand a plurality of abrasive particles, wherein at least a portion ofsaid abrasive particles are fused, crystalline abrasive particlescomprising at least 20 percent by volume, based on the total metal oxidevolume of the respective particle, eutectic colonies, said coloniescomprising a three-dimensional, interpenetrating network of first andsecond crystalline metal oxide phases, said first phase comprising atleast one of crystalline Al₂O₃ or a first, crystalline complexAl₂O₃.metal oxide and said second phase comprising a second, differentcrystalline complex Al₂O₃.metal oxide.
 17. The abrasive articleaccording to claim 16, wherein said article is a coated abrasivearticle, and further comprises a backing.
 18. The abrasive articleaccording to claim 16, wherein said article is a bonded abrasivearticle.
 19. The abrasive article according to claim 16, wherein saidarticle is a nonwoven abrasive article, and further comprises a nonwovenweb.
 20. A vitrified bonded abrasive article comprising a plurality ofabrasive particles bonded together via vitrified bonding material,wherein at least a portion of said plurality of abrasive particles arefused, crystalline abrasive particles comprising at least 20 percent byvolume, based on the total metal oxide volume of the respectiveparticle, eutectic colonies, said colonies comprising athree-dimensional, interpenetrating network of first and secondcrystalline metal oxide phases, said first phase comprising at least oneof crystalline Al₂O₃ or a first, crystalline complex Al₂O₃.metal oxideand said second phase comprising a second, different crystalline complexAl₂O₃.metal oxide.
 21. The vitrified bonded abrasive article accordingto claim 20, wherein said vitrified bonding material comprises silica,alumina, and boria.
 22. The vitrified bonded abrasive article accordingto claim 21, wherein said vitrified bonding material comprises at least10 percent by weight of said alumina.
 23. The vitrified bonded abrasivearticle according to claim 22, wherein said vitrified bonding materialcomprises at least 10 percent by weight of said boria.
 24. A method ofabrading a surface comprising: providing an abrasive article comprisinga binder and a plurality of abrasive particles, wherein at least aportion of said abrasive particles are fused, crystalline abrasiveparticles comprising at least 20 percent by volume, based on the totalmetal oxide volume of the respective particle, eutectic colonies, saidcolonies comprising a three-dimensional, interpenetrating network offirst and second crystalline metal oxide phases, said first phasecomprising at least one of crystalline Al₂O₃ or a first, crystallinecomplex Al₂O₃.metal oxide and said second phase comprising a first,crystalline complex Al₂O₃.metal oxide; contacting at least one of saidfused, crystalline abrasive particles with a surface of a workpiece; andmoving at least one of the contacted fused abrasive particles or saidsurface relative to the other to abrade at least a portion of saidsurface with the contacted fused abrasive particle.
 25. The plurality ofabrasive particles according to claim 1 wherein said specified nominalgrade is selected from the group consisting of ANSI 16, ANSI 24, ANSI36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150,ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400,and ANSI
 600. 26. The plurality of abrasive particles according to claim1 wherein said specified nominal grade is selected from the groupconsisting of P16, P24, P36, P40, P50, P60, P80, P100, P120, P150, P180,P220, P320, P400, P500, P600, P800, P1000, and P1200.
 27. The pluralityof abrasive particles according to claim 1 wherein said specifiednominal grade is selected from the group consisting of JIS16, JIS24,JIS36, JIS46, JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JIS220,JIS240, JIS280, JIS320, JIS360, JIS400, JIS600, JIS800, JIS1000,JIS1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS10,000.
 28. Themethod according to claim 24 wherein said surface is selected from thegroup (if metals consisting of aluminum, carbon steel, mild steel toolsteel, stainless steal, hardened steel, and titanium.
 29. The methodaccording to claim 24 wherein said surface is aluminum.
 30. The methodaccording to claim 24 wherein said surface is carbon steel.
 31. Themethod according to claim 24 wherein said surface is mild steel.
 32. Themethod according to claim 24 wherein said surface is tool steel.
 33. Themethod according to claim 24 wherein said surface is stainless steel.34. The method according to claim 24 wherein said surface is titanium.35. The method according to claim 24 wherein said surface is wood.